Three-Dimensional Photovoltaic Devices Including Non-Conductive Cores and Methods of Manufacture

ABSTRACT

Various stamping methods may reduce defects and increase throughput for manufacturing metamaterial devices. Metamaterial devices with an array of photovoltaic bristles, and/or vias, may enable each photovoltaic bristle to have a high probability of photon absorption. The high probability of photon absorption may lead to increased efficiency and more power generation from an array of photovoltaic bristles. Reduced defects in the metamaterial device may decrease manufacturing cost, increase reliability of the metamaterial device, and increase the probability of photon absorption for a metamaterial device. The increase in manufacturing throughput and reduced defects may reduce manufacturing costs to enable the embodiment metamaterial devices to reach grid parity.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 13/866,387 entitled “Methods for Manufacturing ThreeDimensional Metamaterial Devices with Photovoltaic Bristles” and filedon Apr. 19, 2013, which is a continuation-in-part of U.S. patentapplication Ser. No. 13/830,295 entitled “Methods for ManufacturingThree Dimensional Metamaterial Devices with Photovoltaic Bristles” andfiled on Mar. 14, 2013, the entire contents of which are herebyincorporated by reference. This application is also related to U.S.patent application Ser. No. 13/751,914, entitled “Three-DimensionalMetamaterial Device with Photovoltaic Bristles” filed Jan. 28, 2013, theentire contents of which are hereby incorporated by reference forpurposes of disclosing dimensions, materials and configurations ofphotovoltaic bristles that may be manufactured by the embodimentprocesses disclosed herein.

FIELD

This application generally relates to photovoltaic devices, and morespecifically to the methods of manufacturing photovoltaic cellsfeaturing a large number of photovoltaic bristles.

BACKGROUND

Solar power is a popular clean energy, but it is generally moreexpensive than its fossil fuel competitors (e.g., oil, coal, and naturalgas) and other traditional energy sources (e.g., hydropower). Typically,solar energy is relatively expensive because traditional photovoltaiccells with a planar configuration have generally low total efficiency.Total efficiency is based upon the total power produced from a solarpanel throughout the day as the sun transits across the sky. Totalefficiency is different from the theoretical efficiency, which is thefraction of light energy converted to electricity by the photovoltaiccells with a zero angle of incidence (e.g., the instant when the sun isdirectly above the metamaterial). Thus, a high total efficiencyphotovoltaic cell is needed to make solar energy cost-competitive withfossil fuels and traditional energy sources.

SUMMARY

The various embodiment methods of manufacturing and assembling may beused to produce photovoltaic cells formed from a plurality ofphotovoltaic bristles whose photovoltaic and conductive materials areconfigured to exhibit a high probability of photon absorption andinternal reflection. As a result of the high probability of photonabsorption and internal photon reflections, the photovoltaic cells ofphotovoltaic bristles exhibit high total efficiency in converting lightenergy into electrical energy. The high total efficiency of theembodiment photovoltaic cells may lead to increased efficiency and morepower generation from the photovoltaic cell.

In various embodiments, printing techniques may be used to ensure highthroughput and low defects in manufacturing the metamaterial device. Thehigh throughput and low defects may reduce the manufacturing cost toenable the embodiment metamaterial devices to reach grid parity. Invarious embodiments, arrays of cores or vias may be manufactured from anoriginal master template. An embodiment roll-to-web system and methodmay create daughter templates or master webs from the original mastertemplate to protect the original master template from repeat processing,thereby reducing defects. An embodiment web-to-plate system and methodmay create an array of cores or vias on a substrate from the master web.The master web, or plate, may be subjected to further processing(depositing photovoltaic layers, conductive layers, etc.) to create theembodiment metamaterial device.

In various embodiments, a system for manufacturing a photovoltaicstructure is provided, which may include a web-to-plate systemconfigured to imprint a die including a pattern of protruding structuresonto a moldable material layer to generate a pattern of trenchesextending downward from a top surface of the moldable material layer.The die may be incorporated into a web. The system may further include adeposition system configured to sequentially deposit a transparentconductive material layer, a photovoltaic material layer, and a coreconductive material layer within the pattern of trenches in the moldablematerial layer.

Various embodiments include a method of manufacturing a metamaterial. Insome embodiments a moldable material layer may be provided on, or in, asubstrate. A die including a pattern of protruding structures andincorporated into a web may be imprinted onto the moldable materiallayer to generate a pattern of trenches extending downward from a topsurface of the moldable material layer. A transparent conductivematerial layer, a photovoltaic material layer, and a core conductivematerial layer may be sequentially deposited within the pattern oftrenches in the moldable material layer.

Various embodiments may include a photovoltaic structure. Thephotovoltaic structure includes a dielectric material layer comprising aplanar portion having a uniform thickness and an array of protrudingportions extending from a planar surface of the planar portion. Thephotovoltaic structure further comprises a layer stack located on thedielectric material layer and comprising a core conductive materiallayer, a photovoltaic material layer, and a transparent conductivematerial layer. The core conductive material layer is in contact withthe planar surface and the protruding portions of the dielectricmaterial layer. The transparent conductive material layer is spaced fromthe core conductive material layer by the photovoltaic material layer.Each combination of a protruding portion of the dielectric materiallayer and portions of the layer stack surrounding the protruding portionconstitutes a photovoltaic bristle.

Various embodiments may include a method of forming a photovoltaicstructure. A top surface of a moldable material layer is patterned withan array pattern. The array pattern includes an array of verticallyextending shapes that protrude upward or downward from that top surfaceof the moldable material layer. A layer stack is deposited over thearray pattern. The layer stack comprises a transparent conductivematerial layer, a photovoltaic material layer, and a core conductivematerial layer. A dielectric material layer is deposited over the layerstack. A two-dimensional array of photovoltaic bristles is formed. Eachphotovoltaic bristle comprises a vertically protruding portion of thelayer stack and embedding a dielectric core comprising a dielectricmaterial. The dielectric core contacts a sidewall of the core conductivematerial layer. The transparent conductive material layer is spaced fromthe core conductive material layer by the photovoltaic material layer.

Various embodiments may include a method for manufacturing ametamaterial including an array of photovoltaic bristles havingapproximately cylindrical shapes. An array of vias extending into asubstrate is formed. Each via within the array has an approximatelycylindrical shape and is laterally separated from one another, and islaterally surrounded, by the substrate. A transparent conductive layeris deposited over the array of vias. An absorber layer is deposited overthe outer conductive layer. A core conductive material layer isdeposited over the absorber layer. Each via is partially filled with thecore conductive material layer to form a conductive core of a respectivephotovoltaic bristle. Cavities are filled within the vias by depositinga dielectric material layer over the core conductive material layer. Abase layer is formed over the deposited conductive material. Adielectric core that comprises the dielectric material is formed withineach photovoltaic bristle and between the core conductive material layerand the base layer.

Various embodiments may include a photovoltaic structure that mayinclude a layer stack located over a substrate and may include a coreconductive material layer, a photovoltaic material layer, and atransparent conductive material layer. The photovoltaic structure mayfurther include a plurality of via cavities located underneathvertically protruding portions of the layer stack and above thesubstrate and free of any solid phase material therein.

Various embodiments may include a method of forming a photovoltaicstructure that includes forming a pattern of trenches extending downwardfrom a top surface of an optically transparent layer. A transparentconductive material layer, a photovoltaic material layer, and a coreconductive material layer may be sequentially deposited within thepattern of trenches in the moldable material layer. A via cavitylaterally bound by a surface of the core conductive material layer maybe formed within, or above, each trench.

Various embodiments may include a method for manufacturing ametamaterial including an array of photovoltaic bristles havingapproximately cylindrical shapes. An array of vias extending into asubstrate may be formed. Each via within the array has an approximatelycylindrical shape and is laterally separated from one another, and islaterally surrounded, by the substrate. A transparent conductive layeris deposited over the array of vias. An absorber layer is deposited overthe outer conductive layer. A core conductive material layer isdeposited over the absorber layer. Each via is partially filled with thecore conductive material layer to form a conductive core of a respectivephotovoltaic bristle. A base layer is formed over the depositedconductive material. A non-solid core that does not include theconductive material or a material of the base layer is formed withineach photovoltaic bristle and between the core conductive material layerand the base layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and constitutepart of this specification, illustrate exemplary embodiments of theinvention, and together with the general description given above and thedetailed description given below, serve to explain the features of theinvention.

FIG. 1A is a cross-sectional top view of an embodiment photovoltaicbristle.

FIG. 1B is a cross-sectional side view of an embodiment photovoltaicbristle.

FIG. 2A is a perspective view of an embodiment metamaterial of an arrayof photovoltaic bristles positioned on a flat substrate.

FIG. 2B is a cross-sectional side view of an embodiment metamaterialarray of photovoltaic bristles positioned on a flat substrate.

FIG. 3A is a perspective view of an embodiment metamaterial with arraysof photovoltaic bristles positioned on a corrugated substrate.

FIG. 3B is a cross-sectional side view of an embodiment metamaterialwith arrays of photovoltaic bristles positioned on a corrugatedsubstrate.

FIG. 4A is a perspective view of an embodiment metamaterial with arraysof photovoltaic bristles positioned on alternating slanted substratesurfaces of a corrugated substrate.

FIG. 4B is a cross-sectional side view of an embodiment metamaterialwith arrays of photovoltaic bristles positioned on alternating slantedsubstrate surfaces of a corrugated substrate.

FIG. 5 is an illustration of embodiments shown in FIGS. 2A, 3A, and 4Apositioned on the slanted planes of a structure facing away or towardsthe equator.

FIGS. 6A-6H are cross-sectional side views illustrating an embodimentmethod for forming an array of photovoltaic bristles for a metamaterialdevice stamping process.

FIGS. 6I-6K are cross-sectional side views illustrating an embodimentmethod for forming an array of photovoltaic bristles using a moldingprocess.

FIGS. 7A, 7B, and 7C are side views of a molding process embodiment forforming a substrate and form arrays of cores on the shaped substrate.

FIG. 8 is a process flow diagram illustrating the embodiment methodsillustrated in FIGS. 6A-6K and 7A-7C.

FIGS. 9A-9J are cross-sectional side views illustrating an embodimentmethod of a plating process to form an array of bristles for ametamaterial device.

FIG. 10 illustrates an embodiment plating method for forming theembodiment metamaterials.

FIGS. 11A-11L are cross-sectional side views illustrating an embodimentmethod for forming the embodiment metamaterial by creating vias usingphotolithographic and etching techniques and subsequently removing theoriginal substrate.

FIG. 12 is a process flow diagram illustrating the embodiment method forforming the embodiment metamaterials illustrated in FIGS. 11A-11L.

FIGS. 13A-13L are cross-sectional side views illustrating an embodimentmethod for forming the embodiment metamaterial by creating vias usingphotolithographic and etching techniques while leaving the etchedsubstrate intact.

FIGS. 13M-13O are cross-sectional side views illustrating an alternativeembodiment method for creating vias using lasers.

FIG. 14 is a process flow diagram of the embodiment method illustratedin FIGS. 13A-13L.

FIGS. 15A-15J are cross-sectional side views illustrating an embodimentmethod for forming the embodiment metamaterial by creating vias using astamping method and leaving the substrate intact.

FIGS. 15K-15M are cross-sectional side views for forming the embodimentmetamaterial by molding a substrate and leaving the substrate intact.

FIG. 16 is a process diagram of the embodiment method for forming themetamaterial illustrated in FIGS. 15A-15J.

FIG. 17 is a cross-sectional side view of an array of photovoltaicbristles positioned on a flat substrate with current conducting traceson top of short photovoltaic bristles.

FIG. 18 is a top view of the metamaterial of FIG. 17.

FIG. 19 is a cross-sectional side view of an array of photovoltaicbristles positioned on a flat substrate with current conducting tracesbetween photovoltaic bristles.

FIG. 20 is a top view of metamaterial of FIG. 19.

FIG. 21 is a cross-sectional side view of an array of photovoltaicbristles positioned on a corrugated substrate with current conductingtraces between photovoltaic bristles.

FIGS. 22A-22H are cross-sectional side views illustrating methods foradding current conducting traces to the outer conductive layer of ametamaterial.

FIG. 23 is a process flow diagram of the embodiment method fordepositing current conducting traces on the outer conductive layer of ametamaterial illustrated in FIGS. 22A-22H.

FIGS. 24A-24J are cross-sectional side views illustrating methods foradding current conducting traces to an inner conductive layer of ametamaterial.

FIGS. 24K-24M are cross-sectional side views of methods using a laserprior to adding current conducting traces to an inner conductive layerof a metamaterial.

FIG. 25 is a process flow diagram of the embodiment method fordepositing current conducting traces on an inner conductive layer of ametamaterial illustrated in FIGS. 24A-24J.

FIG. 26 is a perspective view of embodiment metamaterials in a solarpanel section including a corrugated base.

FIG. 27 is a top view of a section of a solar panel with a corrugatedbase according to an embodiment.

FIG. 28 is a side view of a section of a solar panel with a corrugatedbase according to an embodiment.

FIG. 29 is an exploded view of a section of a solar panel with acorrugated base according to an embodiment.

FIG. 30 is a back view of a section of a solar panel with a corrugatedbase according to an embodiment.

FIG. 31 is a perspective view of a solar panel according to anembodiment.

FIG. 32 is an exploded view of a solar panel according to an embodiment.

FIGS. 33A-33G are cross-sectional side views illustrating an embodimentmethod for forming an array of photovoltaic bristles for a metamaterialdevice stamping process.

FIG. 34 is a process flow diagram illustrating the embodiment methodillustrated in FIGS. 33A-33G.

FIG. 35A is a system diagram illustrating an embodiment roll-to-websystem.

FIGS. 35B-35E are logic diagrams corresponding to the roll-to-web systemillustrated in FIG. 35A.

FIG. 36A is a system diagram illustrating an embodiment web-to-platesystem.

FIGS. 36B-36E are logic diagrams corresponding to the web-to-platesystem illustrated in FIG. 36A.

FIGS. 37A-37E are sequential vertical cross-sectional views of a firstexemplary photovoltaic structure during a manufacturing processaccording to an embodiment.

FIG. 37F is a magnified vertical cross-sectional view of the firstexemplary photovoltaic structure of FIG. 37E.

FIG. 37G is a magnified vertical cross-sectional view of anotherembodiment of the first exemplary photovoltaic structure.

FIG. 37H is a perspective view of the first exemplary photovoltaicstructure of FIG. 37E.

FIG. 37I is a magnified vertical cross-sectional view of yet anotherembodiment of the first exemplary photovoltaic structure.

FIG. 37J is a magnified vertical cross-sectional view of still anotherembodiment of the first exemplary photovoltaic structure.

FIG. 37K is a magnified vertical cross-sectional view of anotherembodiment of the first exemplary photovoltaic structure.

FIG. 37L is a magnified vertical cross-sectional view of anotherembodiment of the first exemplary photovoltaic structure.

FIG. 37M is a magnified vertical cross-sectional view of anotherembodiment of the first exemplary photovoltaic structure.

FIG. 37N is a magnified vertical cross-sectional view of anotherembodiment of the first exemplary photovoltaic structure.

FIGS. 38A-38E are sequential vertical cross-sectional views of a secondexemplary photovoltaic structure during a manufacturing processaccording to an embodiment.

FIG. 38F is a perspective view of the second exemplary photovoltaicstructure of FIG. 38E.

FIG. 39 is a system diagram illustrating an embodiment web-to-platesystem.

FIG. 40 is an illustration of a system for manufacture of a photovoltaicstructure according to an embodiment.

FIGS. 41A-41B are sequential vertical cross-sectional views of a thirdexemplary photovoltaic structure during a manufacturing processaccording to an embodiment.

FIG. 41C is an exploded view of the third exemplary photovoltaicstructure according to an embodiment.

FIG. 41D is a see-through perspective view of the third exemplaryphotovoltaic structure according to an embodiment.

FIGS. 41E-41I are alternate embodiments of the third exemplaryphotovoltaic structure.

FIGS. 42A-42B are sequential vertical cross-sectional views of a fourthexemplary photovoltaic structure during a manufacturing processaccording to an embodiment.

FIGS. 43A-43C are sequential vertical cross-sectional views of a fifthexemplary photovoltaic structure during a manufacturing processaccording to an embodiment.

FIG. 43D is an exploded view of the fifth exemplary photovoltaicstructure according to an embodiment.

FIG. 43E is a see-through perspective view of the fifth exemplaryphotovoltaic structure according to an embodiment.

FIG. 44A is a vertical cross-sectional view of the fifth exemplaryphotovoltaic structure of FIG. 43C.

FIG. 44B is a vertical cross-sectional view of another embodiment of thefifth exemplary photovoltaic structure.

FIG. 44C is a vertical cross-sectional view of yet another embodiment ofthe fifth exemplary photovoltaic structure.

FIG. 45 is a vertical cross-sectional view of a sixth exemplaryphotovoltaic structure.

DETAILED DESCRIPTION

The various embodiments will be described in detail with reference tothe accompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.References made to particular examples and implementations are forillustrative purposes, and are not intended to limit the scope of theinvention or the claims. Any reference to claim elements in thesingular, for example, using the articles “a,” “an,” or “the” is not tobe construed as limiting the element to the singular. The terms“example,” “exemplary,” or any term of the like are used herein to meanserving as an example, instance, or illustration. References toparticular examples and implementations are for illustrative purposes,and are not intended to limit the scope of the invention or the claims.Any implementation described herein as an “example” is not necessarilyto be construed as preferred or advantageous over anotherimplementation. The drawings are not drawn to scale. Multiple instancesof an element may be duplicated where a single instance of the elementis illustrated, unless absence of duplication of elements is expresslydescribed or clearly indicated otherwise.

The various geometrical features of the embodiment photovoltaicstructures are described herein with reference to spatial orientations(e.g., top, bottom, horizontal, vertical, etc.) of the photovoltaicstructures (such as an upright orientation or an inverted orientation)as illustrated in the figures. Such references to special orientationsof the various features described or recited in claims is for ease ofdescription with reference to the figures, and are not intended toimpose limits or requirements on the finished product produced by thevarious embodiment methods. Thus, references to horizontal and verticalare merely with reference to the orientation of structures illustratedin the figures, and not intended to impose limits or restrictions on themanner or orientation in which the structures may be deployed. Forexample, an embodiment of the structures formed by the embodimentfabrication methods orients the finished product so that the conicalshapes described as having a vertical dimension are deployed at an angleto the vertical with respect to the ground.

As used herein, the term “photovoltaic bristle” refers to athree-dimensional structure approximately cylindrical with a heightapproximately equal to 1-100 microns, a diameter of approximately 0.2-50microns that includes at least one photovoltaically-active semiconductorlayer sandwiched between a conductive inner layer or core and atransparent outer conductive layer (e.g., TCO and a nonconductive outerlayer). The term “bristle” is used merely because the structures have alength greater than their diameter, the structures have a generally (onaverage) circular cross-section, and the overall dimensions of thestructures are on the dimensions of sub-microns to tens of microns. Inthe embodiment illustrated herein the photovoltaic bristles have anapproximately cylindrical shape, by which it is meant that a substantialportion of the exterior surface of the structures have a cross-sectionthat is approximately circular or elliptical with both radii beingapproximately coexistent. Due to manufacturing variability, no singlephotovoltaic bristle may be exactly cylindrical in profile, but whenconsidered over a large number of photovoltaic bristles the averageprofile is approximately cylindrical. In another embodiment, thephotovoltaic bristles may have a non-circular cross-section, such ashexagonal, octagonal, elliptical, etc. as may facilitate manufacturing.

When the embodiment photovoltaic bristles are arranged on a substrate inan order or disordered array, the resulting structure may form ametamaterial structure. As used herein, the term “metamaterial” or“metamaterial substrate” refers to an array of photovoltaic bristles ona substrate. Metamaterials as used herein are artificial materials thatare engineered with metals or polymers that are arranged in a particularstructured or non-structured pattern that result in material properties(including light absorption and refraction properties) that aredifferent from the component materials. The cumulative effect of lightinteracting with the array of photovoltaic bristles may be affected bycontrolling the shape, geometry, size, orientation, material properties,material thicknesses, and arrangement of the bristles making up themetamaterial as described herein.

As used herein, a “layer” refers to a material portion including aregion having a substantially uniform thickness. A layer may extend overthe entirety of an underlying or overlying structure, or may have anextent less than the extent of an underlying or overlying structure.Further, a layer may be a region of a homogeneous or inhomogeneouscontiguous structure that has a thickness less than the thickness of thecontiguous structure. For example, a layer may be located between anypair of horizontal planes between, or at, a top surface and a bottomsurface of the contiguous structure.

Traditional planar photovoltaic cells are flat. In traditional planarphotovoltaic cells, a limited number of photons are absorbed at anygiven point in time. Photon absorption occurs through the thickness ofthe traditional planar photovoltaic cell (e.g., top-to-bottom) from thepoint of photon entry until the photon is converted to electricalenergy. Traditional planar photovoltaic cells convert photons intoelectrical energy when photons interact with a photovoltaic layer.However, some photons pass through the photovoltaic layer withoutgenerating electron-hole pairs, and thus represent lost energy. Whilethe number of photons absorbed may be increased by making thephotovoltaic layer thicker, increasing the thickness increases thefraction of electron-hole pairs that recombine, converting theirelectrical potential into heat. Additionally, thicker photovoltaic filmsexhibit an exponential attenuation loss, which leads to a decrease inphoton conversion. For this reason, traditional planar photovoltaiccells have emphasized thin photovoltaic layers, accepting the reducedphoton-absorption rate in favor of increased conversion of electron-holepairs into electrical current and reduced heating. The theoretical peakefficiency, as well as the total efficiency of traditional planarphotovoltaic cells is thus limited by the planar geometry and theunattenuated fraction of photons that may be absorbed in a maximizedoptical path length through the photovoltaic layer.

Conventional planar photovoltaic cells also suffer from low totalefficiency in static deployments (i.e., without sun tracking equipment)since their instantaneous power conversion efficiency decreasessignificantly when the sun is not directly overhead (i.e., before andafter noon). Peak efficiencies of traditional planar photovoltaic cellsare affected by their orientation with respect to the sun, which maychange depending on the time of day and the season. The standard testconditions for calculating peak efficiencies of solar cells are based onoptimum conditions, such as testing the photovoltaic cells at solar noonor with a light source directly above the cells. If light strikestraditional photovoltaic cells at an acute angle to the surface (i.e.,other than perpendicular to the surface) the instantaneous powerconversion efficiency is much less than the peak efficiency. Traditionalplanar photovoltaic cells in the northern hemisphere are typicallytilted toward the south by an angle based on the latitude in order toimprove their efficiency. While such fixed angles may account for theangle of the sun at noon due to latitude, the photovoltaic cells receivesunlight at an angle during the morning and afternoon (i.e., most of theday). Thus, traditional planar photovoltaic cells actually result in alow total efficiency and low total power generation when measured beyonda single moment in time.

The various embodiments include photovoltaic cells that exhibitmetamaterial characteristics from regular or irregular arrays ofphotovoltaic bristles configured so the conversion of light intoelectricity occurs within layers of the photovoltaic bristles. Since thephotovoltaic bristles extend above the surface of the substrate and arespaced apart, the arrays provide the photovoltaic cells of the variousembodiments with volumetric photon absorption properties that lead toenergy conversion performance that exceeds the levels achievable withtraditional planar photovoltaic cells. The volumetric photon absorptionproperties enable the various embodiment photovoltaic cells to generatemore power than traditional planar photovoltaic cells with the samefootprint. Due to the small size of the photovoltaic bristles, thephotovoltaically-active layers within each bristle are relatively thin,minimizing power losses due to electron-hole recombination. The thinphotovoltaically-active layers help reduce attenuation losses normallypresent in thicker photovoltaic films because the photovoltaic bristlesinclude a thin radial absorption depth and a relatively thicker verticalabsorption depth maximizing photon absorption and power generationthrough the combined long circumferential absorption path length andshort radial electron path length. When individual photovoltaic bristlesare combined in an array on or within a substrate, a metamaterialstructure may be formed that exhibits a high probability of photonabsorption and internal reflection that leads to increased energyconversion efficiencies and power generation. Various embodimentstructures also provide additional performance-enhancing benefits aswill be described in more detail below.

Further performance enhancements may be obtained by positioning theembodiment photovoltaic cells so that the photovoltaic bristles'sidewalls are at an angle to the incident photons. This may improve theprobability that photons will be absorbed into the photovoltaic bristlesdue to wave interactions between photons and the outer conductive layeron each photovoltaic bristle. Orienting the embodiment photovoltaicbristles at an angle to the incident photons also increases thecircumferential optical depth of the photovoltaic bristles exposed tothe light, because in such an orientation the photons strike the sidesof the bristles and not just the tops of the bristles. The off-axisphoton absorbing characteristics of the photovoltaic bristles alsoenables the embodiment photovoltaic cells to exhibit significant totalenergy conversion efficiency for indirect and scattered light, therebyincreasing the number of photons available for absorption compared to aconventional photovoltaic cell.

An embodiment described herein includes photovoltaic cells featuringarrays of photovoltaic bristles on roughly corrugated surfaces in orderto present the bristles at an angle to incident sunlight. Furtherembodiments described herein include methods for manufacturingphotovoltaic cells featuring arrays of photovoltaic bristles, as well asassembly of such photovoltaic cells into solar panels.

For purposes of background on the physics and geometries that enablephotovoltaic bristles to achieve significant improvements in peak powerperformance, an overview of embodiment photovoltaic bristles andcorresponding photovoltaic cells is now presented. More details on thedimensions, materials and configurations of embodiment photovoltaicbristles are disclosed in U.S. patent application Ser. No. 13/751,914that is incorporated by reference above.

FIG. 1A illustrates a cross-sectional top view of one photovoltaicbristle 101 and FIG. 1B illustrates a cross-sectional side view of thephotovoltaic bristle 101 of FIG. 1A. FIGS. 1A and 1B illustrate the pathtraveled by a photon entering the side of the outer periphery of thephotovoltaic bristle 101. A photovoltaic bristle 101 may guide anabsorbed photon 112 so that it follows an internal path 113 thatexhibits a high probability that the photon remains within thephotovoltaic bristle 101 due to total internal reflection. Aphotovoltaic bristle may exhibit total internal reflection bycontrolling the thickness of the layers 103 and 111 and by radiallyordering the materials by indexes of refractions from a low index ofrefraction on the outside to a higher index of reaction in each innerlayer, the photovoltaic bristle 101 may refract or guide photons 112toward the core of the photovoltaic bristle 101. Since the core 106 maybe highly conductive, it is also highly reflective, so that it willreflect photons 112. As illustrated, due to the large difference inindex of refraction between the absorber layer and the outer conductivelayer 103, photons striking this boundary at an angle will be refractedinward. As a result of these reflections and refractions, photons 112may be effectively trapped within the absorption layer 111 for a longerperiod of time, thereby increasing the probability of interaction withthe absorption layer 11 causing an electron-hole pair to be formed.Increasing the probability of photon absorption may result in moreelectrical current being generated for the same amount of incident lightenergy by the embodiment photovoltaic cells than is achievable byconventional photovoltaic cells.

It should be noted that the embodiment shown in FIGS. 2A-2B may includean inner reflector due to a metal core 106. In other embodiments, arefraction layer may be applied over the core 106 to achieve the samephoton reflection effects. In such an embodiment, a reflective layer maybe formed over the conductive core and under the absorber layer, such asa semiconductor or dielectric material layer having a lower index ofrefraction than the absorber layer. This refraction layer may beconfigured to reflect the photon at the interface between the reflectionlayer and the absorber layer, and not rely on reflection off of theconductive core 106. For example, such a diffraction layer may be formedfrom an aluminum doped zinc oxide layer of about 500-1500 angstroms inthickness. Reflected photons then refract through each layer 104, 105until they reach the outer conductive layer 103, where the difference inthe index of refraction between the absorption sublayer 105 and theouter conductive layer 103 causes the photons to reflect back into theabsorption layers of the photovoltaic bristle. The reflected photonsthat are not reflected inwardly at the boundary between the outerconductive layer 103 and the absorption sublayer 105 may pass throughthe outer conductive layer 103 and be reflected off of the interfacebetween the outer conductive layer 103 and air due to the difference inthe index of refraction at this interface. In either manner, photons mayremain within the photovoltaic bristle passing back and forth throughthe absorption layer 111 until they are eventually absorbed or exit thebristle.

Each photovoltaic bristle 101 is made up of a core 106 that may beconductive or has a conductive outer surface, an absorption layer 111and an outer conductive layer 103, which will typically be a transparentconductive layer such as a transparent conductive oxide or transparentconductive nitride. Due to the cylindrical form of photovoltaicbristles, the absorption layer 111 surrounds the core 106, and the outerconductive layer 103 surrounds the absorption layer 111. Although, twoabsorber sublayers 104, 105 are shown, it should be noted that theabsorption layer 111 may include any number of absorber sublayers orregions of photovoltaically-active materials or combinations ofphotovoltaic materials. For example, the absorption layer 111 mayinclude multiple absorber sublayers or regions that form a p-n junction,a p-i-n junction, or multi junction regions, which have a generallycircular cross-section as illustrated in FIG. 1A. If the absorptionlayer 111 forms a p-i-n junction with three absorber sublayers, onesublayer may be the intrinsic portion forming the p-i-n junction. If thecore 106 is a semiconductor core forming a p-n junction with a singleabsorber sublayer, the absorption layer 111 may include only onesublayer. Regardless of the number, the absorber sublayers or regions104, 105 may be made from one or more of silicon, amorphous silicon,polycrystalline silicon, single crystal silicon, cadmium telluride,gallium arsenide, aluminum gallium arsenide, cadmium sulfide, copperindium selenide, and copper indium gallium selenide.

The relative radial positions of the p-type, intrinsic, or n-typesublayers/regions may vary in different embodiments. For example, in anembodiment the p-type semiconductor material may be positioned radiallyinside the n-type semiconductor material. In another embodiment, then-type semiconductor material may be positioned radially inside thep-type semiconductor material. In addition, multiple materials may beused to create a sequence of p-n and/or n-p junctions, or p-i-njunctions in the absorption layer. For example, the absorption layer mayinclude an absorber sublayer of p-type cadmium telluride (CdTe) and anabsorber sublayer of n-type cadmium sulfide (CdS). In an embodiment, theabsorption layer 111 may be fully depleted. For example, the p-typeregion and the n-type region forming the sublayer or region 104 and thesublayer or region 105 may be fully depleted.

In an example embodiment, the absorption layer 111 may include a p-typesemiconductor sublayer 105, such as p-type cadmium telluride, and ann-type semiconductor sublayer of a different material, such asn-type-cadmium sulfide. In another example embodiment, one sublayer 104may be a p-type region, such as p-type amorphous silicon, and anothersublayer 105 may be an n-type region of the same material as thesublayer 104 but doped to form an n-type semiconductor, such as n-typeamorphous silicon.

The outer conductive layer 103 has a radial thickness which may bemeasured radially from the outer surface of the absorption layer 111 tothe outer surface of the outer conductive layer 103 (i.e., the outersurface of the photovoltaic bristle). In an embodiment, the outerconductive layer 103 is a transparent conductive oxide (“TCO”), such asa metal oxide. In an embodiment, the outer conductive layer 103 mayinclude a dopant creating a p-type or n-type transparent conductiveoxide. For example, the transparent conductive oxide layer 103 may beone of intrinsic zinc oxide, indium tin oxide, and cadmium tin oxide(Cd2SnO4). In an embodiment, the outer conductive layer 103 may includea transparent conductive nitride such as titanium nitride (TiN). Inanother embodiment, the outer conductive layer 103 may include a bufferwith or without the dopant. Some examples of an outer conductive layer103, which may be a transparent conductive oxide with a dopant, includeboron-doped zinc oxide, fluorine doped zinc oxide, gallium doped zincoxide, and aluminum doped zinc oxide. Some examples of buffers that maybe added to a transparent conductive oxide include zinc stannate(Zn2SnO4), titanium dioxide (TiO2), and similar materials well known inthe art.

Although not shown in FIGS. 1A-1B, the outer conductive layer 103 mayinclude any number of conductive and/or non-conductive sublayers toachieve a particular total optical thickness while simultaneously havinga thin conductive sublayer. With multiple sublayers, the outerconductive layer 103 may also benefit from adding flexibility to thephotovoltaic bristles for a more resilient photovoltaic bristlemetamaterial device. The addition of a non-conductive sublayer may haverefractive properties that improve off-angle photon absorptionefficiency. Analysis and observations of prototypes indicate that outerconductive layers between 500 and 15,000 angstroms result in a decreasein electrical resistance in the conductive layers from field effects atthe structural discontinuities in the photovoltaic bristles. However,the outer conductive layer 103 of a bristle may need to be of a minimumoptical thickness exceeding 500 angstroms to achieve the photon trappingand guiding effect shown in FIG. 1A. Thus, the outer conductive layer103 may include multiple layers to achieve the conflicting opticalthickness requirement and the requirement for electrical resistivitybenefits from field effects. As an example, the outer conductive layer103 may have two sublayers including a conductive sublayer such TCO anda non-conductive sublayer such as an optically transparent polymer. Asanother example, the non-conductive sublayer may be a bi-layer includingTCO and a polymer or glass. As a further example, the outer conductivelayer 103 may include three sublayers where a non-conductive sublayerseparates two conductive sublayers.

In an embodiment, the core 106 may be of a variety of conductivematerials and non-conductive materials. In an embodiment, the core 106may be a solid conductive core such as a metal. For example, the solidconductive core may be gold, copper, nickel, molybdenum, iron, aluminum,or silver. In an embodiment, the core 106 may include the same materialas the substrate 202 (shown in FIG. 2B). For example, the core 106 andthe substrate 202 may include a polymer. In another embodiment, the core106 may include a different material than the substrate 202. In anotherembodiment, an inner conductive layer 107 may surround the core 106. Forexample, the inner conductive layer 107 may be gold, copper, nickel,molybdenum, iron, aluminum, or silver to create a conductive core. In anembodiment, the core 106 may include a polymer with an inner conductivelayer 107 surrounding the polymer. The inner conductive layer 107 mayinclude similar material as the outer conductive layer 103. For example,the inner conductive layer 107 may include a transparent conductiveoxide, a transparent conductive nitride, and/or a non-conductivetransparent material. The inner conductive layer 107 may includemultiple layers (e.g., sublayers of TCO and a non-conductive opticallytransparent polymer) to achieve the conflicting benefits of fieldeffects and proper optical depth for the photovoltaic device. In anembodiment, the core 106 may include a semiconductor material. Forexample, the core 106 may be made from one or more of silicon, amorphoussilicon, polycrystalline silicon, single crystal silicon, cadmiumtelluride, gallium arsenide, aluminum gallium arsenide, cadmium sulfide,copper indium selenide, and copper indium gallium selenide.

FIG. 1B also illustrates that photons striking the photovoltaic bristle101 will have a higher probability of absorption when they strike thesidewall of a photovoltaic bristle at a compound angle that is less than90 degrees but more the 0 degrees to the surface, where an angleperpendicular to the sidewall surface is considered to be 0 degrees. Thecompound incident angle includes a vertical plane component 133 (shownin FIG. 1B) and a horizontal plane component 132 (shown in FIG. 1A). Thehorizontal plane component 132 is defined by a photon 112 striking theouter surface of the bristle at a point along the perimeter of thecircular cross-section plane forming an angle with the perimeter wherean angle perpendicular to the perimeter is considered 0 degrees.Similarly, the vertical plane component 133 is defined by the photon 112striking the outer surface of the bristle at a point along the heightforming a vertical angle with the surface where an angle perpendicularto the surface is considered 0 degrees.

Analysis of photon absorption characteristics of the outer conductivelayer have revealed that photons striking the surface of the sidewall ofthe photovoltaic bristle perpendicular to the horizontal component 132and the vertical component 133 may result in a compound angle of 0degrees and an increased probability of being reflected off the surface.Similarly, photons striking the surface of the sidewall of thephotovoltaic bristle parallel to the vertical and the horizontalcomponent will also have an increased probability of being reflected offthe surface. However, photons striking the side surface at a compoundangle between 10° and 80° have a high probability of being absorbed intothe outer conductive layer 203. Once absorbed, the internal refractioncharacteristics of the absorber sublayers 104, 105 and outer conductivelayer 103 cause the photons to remain within the photovoltaic bristle101 for an extended time or path length. This characteristic is verydifferent from conventional photovoltaic cells, which exhibit themaximum power conversion efficiency when the angle of incidence ofphotons is normal to its single planar surface.

The difference between the incident angle corresponding to conventionalphotovoltaic cells and the photovoltaic bristles is illustrated by angleθp in FIG. 1B. The preferred incident angle for a traditional solarcell, Op, would form a right angle with the top of the bristle as wellas the substrate of the full metamaterial device (not shown). Thus, notonly does the photovoltaic bristle exhibit better absorptioncharacteristics at off-angles (not perpendicular or parallel to thesurface), the reference point for measuring an off-angle is differentfrom that of a conventional photovoltaic cells. For a metamaterialdevice with photovoltaic bristles, the reference point is measured fromthe sidewall of a bristle in two planes, which is unachievable by aplanar photovoltaic cell. Thus, due to the off-angle absorptioncharacteristics of photovoltaic bristles, the embodiment photovoltaiccells exhibit significant power conversion efficiency across a broadrange of angle of incidence. This translates to more power generationthroughout the day than achievable from fixed solar panels withconventional planar solar arrays that produce their peak efficiencies(i.e., maximum power generation) when the sun is directly overhead.

FIG. 2A illustrates a perspective view of metamaterial 200 including anarray of photovoltaic bristles 201 a, 201 b, 201 c, 201 d, 201 e, 201 f,201 g, 201 h, 201 i, 201 j, 201 k, 201 l, 201 m, 201 n, 201 o, 201 pextending from a flat substrate 202 (shown in FIG. 2B). Whileillustrated with twelve photovoltaic bristles 201 a-201 p, ametamaterial may include a larger number of photovoltaic bristles. Thenumber of photovoltaic bristles 201 will depend upon the dimensions andspacing of the bristles and the size of the photovoltaic cell. As withconventional photovoltaic cells, metamaterials may be assembled togetherin large numbers to form panels (i.e., solar panels) of a size that aresuitable for a variety of installations.

Each photovoltaic bristle 201 a-201 p is characterized by its height“h,” which is the distance that each bristle extends from the substrate202. Photovoltaic bristles 201 a-201 p are also characterized by theirradius “r”. In an embodiment, all photovoltaic bristles 201 a-201 pwithin an array will have approximately the same height h andapproximately the same radius r in order to facilitate manufacturing.However, in other embodiments, photovoltaic bristles 201 a-201 p withinthe array may be manufactured with different heights and diameters.

In an embodiment, the number of photovoltaic bristles in a photovoltaiccell may depend upon the substrate surface area available within thecell and the packing density or inter-bristle spacing. In an embodiment,photovoltaic bristles may be positioned on the substrate with a packingdensity or inter-bristle spacing that is determined based upon thebristle dimensions (i.e., h and r dimensions) as well as otherparameters, and/or pattern variations. For example, a hexagonal patternmay be used rather than the trigonometric pattern shown in FIG. 2A.

In the various embodiments, the dimensions and the inter-bristle spacingof photovoltaic bristles may be balanced against the shading ofneighboring bristles. In other words, increasing the number ofphotovoltaic bristles on a plane may increase the surface area availablefor absorbing photons. However, each photovoltaic bristle casts a smallshadow, so increasing the photovoltaic bristle density of a photovoltaiccell beyond a certain point may result in a significant portion of eachbristle being shadowed by its neighbors. While such shadowing may notreduce the number of photons that are absorbed within the array,shadowing may decrease the number of photons that are absorbed by eachphotovoltaic bristle, and thus there may be a plateau in the photonabsorption versus packing density of photovoltaic bristles.

A further consideration beyond shadowing is the wave interaction effectsof the array of closely packed photovoltaic bristles. Theinterior-bristle spacing may be adjusted to increase the probabilitythat photons entering the array are absorbed by the photovoltaicbristles' metamaterial properties considering the bulk materialproperties of the layered films that makeup the array. For example,specific characteristics such as extinction coefficient or absorptionpath length may predict an optimal dimensional design, although one maychoose to deviate from this prediction resulting in a sacrifice inperformance.

FIG. 2B is a cross-sectional side view of a section of metamaterial 200including photovoltaic bristles 201 m, 201 n, 201 o, and 201 p asillustrated in FIG. 2A. As shown in FIG. 2B the photovoltaic bristlesextend from a substrate 202. In an embodiment, the core 106 may be thesame material as the substrate 202 and an inner conductive layer 107 maysurround the core 106. The absorber layer 111 may surround the innerconductive layer 107 and the outer conductive layer 103 may surround theabsorber layer 111. The absorber layer 111 may include any number ofsublayer or regions. As illustrated in FIG. 2B, the absorber layer 111may include two sublayers or regions 104, 105. In an embodiment, the twoabsorber sublayers or regions 104, 105 may be any semiconductor materialwhere one sublayer or region is doped as n-type and the other is dopedas p-type.

The metamaterial 200 may include a substrate 202 of any suitablesubstrate material known to one skilled in the art. For example, thesubstrate 202 may be glass, doped semiconductor, diamond, metal, apolymer, ceramics, or a variety of composite materials. The substrate202 material may be used elsewhere in the metamaterial 200, such as amaterial used in any layer of a photovoltaic bristle 201 m-201 n.Alternatively, the material used in the substrate 202 may be differentfrom other materials used in the photovoltaic bristles 201 m-201 n. Inan embodiment, the core 106 and the substrate 202 may include a commonmaterial. For example, the substrate 202 and the core 106 may includeglass, semiconductor material, a polymer, ceramics, or composites. In afurther embodiment, the core 106 and substrate 202 may include similarmaterials, while the inner conductive layer 107 is added over thesubstrate 202 and surrounding the core 106 creating a conductive core.The inner conductive layer 107 may include metal such as gold, copper,nickel, molybdenum, iron, aluminum, or silver. Alternatively, the innerconductive layer may include any of the materials used for the outerconductive layer 103 which may be used in combination with thepreviously listed metals.

In an embodiment, the inner conductive layer 107 may also be an innerrefraction or reflection layer that is added on top of the core 106 inorder to provide an inner reflection interface for photons. In thisembodiment, a layer of semi-conductive or insulator material, such asB:ZnO, Al:ZnO, ZnO, or ITO, may be applied over the metal core. Thislayer may be at least one-half wavelength in thickness, depending on therefractive index of the material. For example, such a layer made ofAl:ZnO (AZO) may be approximately 500 angstroms to 1500 angstroms thickover which the absorber layer may be applied. Such an AZO layer has arefractive index that is lower than the absorber layer. This differencein refractive index coupled with the curvature of the interface of thesetwo layers will reflect the photons before they reach the metal core.The reflection induced by this design may exhibit lower losses than thedesigns in which photons reflect from a metal surface of the core. Theuse of such a refraction layer may be included in any of the embodimentsillustrated and described herein. For example, in the embodiments inwhich the center of the core is a plastic rod, a metal layer is appliedover the plastic core and then the AZO is applied over the metal layer.In further embodiments, this refractive layer forming a reflectinginterface may be formed using multiple layers, such as: ITO-AZO;ITO-AZO-ITO; TiO2-TiN—TiO2; ZnO-AZO-ZnO; etc. Such multiple layers mayfunction similar to a Bragg reflector used in fiber optics.

In order to increase the percentage of solar photons strikingphotovoltaic bristles at the appropriate angle of incidence, oneembodiment orients the photovoltaic bristles at an angle on a corrugatedsubstrate. Positioning photovoltaic bristles at an angle to incidentlight increases the probability of off-axis photon absorption, which mayreflect and propagate photons around and within the photovoltaicbristles, thereby developing an equilibrium standing wave and increasingprobability of converting photon energy into electrical energy.Consequently, embodiment photovoltaic cells with such a corrugated shapemay generate more electrical power than is possible from conventionalphotovoltaic cells.

In addition to increasing the probability of photon absorption,embodiment corrugated photovoltaic cells provide more surfaces and morephotovoltaic bristles for photon absorption within a given planarfootprint than a comparable flat substrate configuration. Eachcorrugated photovoltaic cell may include a large number of angledsurfaces with photovoltaic bristles, compared to a conventional flatsubstrate photovoltaic cell that has only a single flat surface orabsorbing photons. The improvements from the corrugated photovoltaiccell results in an increase in optical volume enabling more photonabsorption and power generation from such a metamaterial device.

FIG. 3A is a perspective view of an embodiment metamaterial 300including a corrugated shaped substrate 302 (shown in FIG. 3B) witharrays of photovoltaic bristles 301 positioned on each slanted substratesurface 308 a, 308 b, 308 c, 309 a, 309 b, and 309 c. Although FIG. 3Adepicts six slanted substrate surfaces, in an embodiment, themetamaterial 300 may have a larger number of slanted substrate surfaces.In FIG. 3A, each slanted substrate surface 308 a-308 c, and 309 a-309 cmay form an angle θb with the flat foundation 303 of the substrate 302.In an embodiment angle θb may be between about 30 and about 60 degrees.In further embodiments the angle θb may be 30-35 degrees, 35-40 degrees,40-45 degrees, 45-50 degrees, 50-55 degrees, and 55-60 degrees. In anembodiment, arrays of photovoltaic bristles 301 may be oriented so thattheir long axis is normal to the slanted substrate surfaces 308 a-308 cand 309 a-309 c including angle θb to increase the probability of photonabsorption and photon trapping and guiding from photons striking thesidewalls of each photovoltaic bristles 301 at compound anglesapproximately between 10 and 80. It should be noted that each slantedsubstrate surface 308 a-308 c and 309 a-309 c may include any number ofphotovoltaic bristles 301 (i.e. more than the twelve photovoltaicbristles 301 shown in the figure).

FIG. 3B is a cross-sectional side view of a section of a metamaterial300 including slanted substrate surfaces 308 a and 309 a at angles θbwith the foundation 303 and an array of photovoltaic bristles 301 oneach slanted substrate surface. As described above, each photovoltaicbristle 301 may include a core 106, an inner conductive layer 107, andan absorber layer 111 with absorber sublayers 104, 105 surrounding theinner conductive layer, and an outer conductive layer 103 surroundingthe absorber layer 111. In an embodiment, the core 106 may be the samematerial as the substrate 302. The photovoltaic bristles 301 extend fromthe corrugated surface 302 perpendicular to each slanted surface 308,309. As illustrated in the figure, this angle enables photons 112traveling along the photon path 113 to enter the sidewall of thephotovoltaic bristle 301 at a compound angle of approximately 10°-80°.

In another embodiment, photovoltaic bristles are positioned only onalternating slanted surfaces of the corrugated substrate, with theopposite surfaces lacking such structures. This embodiment configurationmay reduce manufacturing costs while presenting photovoltaic bristles onthe surfaces most likely to receive solar radiation when deployed.Additionally, the slanted surfaces that do not include photovoltaicbristles may be coated with a reflective material (e.g., a metal) sothat photons striking that surface are reflected at a desirable angleinto the photovoltaic bristles on the opposite surface. Such anembodiment is illustrated in FIGS. 4A and 4B.

FIG. 4A is a perspective view of metamaterial 400 including a corrugatedshaped substrate 402 (shown in FIG. 4B) and arrays of photovoltaicbristles 401 positioned at normal from the planes of alternating slantedsubstrate surfaces 408 a, 408 b, and 408 c. In an embodiment, slantedsubstrate surfaces 409 a, 409 b, and 409 c may be without arrays ofphotovoltaic bristles 401 and may be configured with a reflectivesurface coating, such as a metal, that may reflect photons into thephotovoltaic bristles on the opposite surface as illustrated in FIG. 4B.Although FIG. 4A depicts six slanted substrate surfaces, in anembodiment, the metamaterial 400 may have a larger or smaller number ofslanted substrate surfaces.

FIG. 4B is a cross-sectional side view of a section of metamaterial 400with a corrugated substrate 402 including slanted substrate surfaces 408a, 408 b, 409 a, 409 b at angles θb with the foundation 403. In anembodiment, each slanted substrate surface 408 a, 408 b may include anarray of photovoltaic bristles 401 configured approximately normal tothe slanted substrate surface. In an embodiment, slanted substratesurfaces 409 a and 409 b may include a reflective layer 405. As such,the reflective layer 405 may reflect photons 411 along a photon path 412so that the reflected photons 411′ strikes the photovoltaic bristlesextending from the adjacent slanted substrate surface 408 b of thesubstrate 402. In an embodiment, a reflective layer 405 (i.e.,reflective film) may be any material that has high reflectivecharacteristics to reflect photons usable for the embodied metamaterial.

FIG. 5 illustrates an advantage of the various embodiment photovoltaiccells when installed on a typical structure 502 (e.g., a house) having aroof with angled surfaces 504, 506. In this illustrative figure,photovoltaic cells 200 on a northern facing roof surface may have a flatprofile and feature photovoltaic bristles 201 that extend perpendicularfrom the surface. Since this surface of the roof 506 receives sunlightat an angle, the incident sunlight on this surface is preferable forincreasing photon absorption on such a photovoltaic cell 200. On thesouthern facing roof surface 504, corrugated photovoltaic cells 300, 400may be used since the sunlight will be striking the roof surface 504 atcloser to a perpendicular angle of incidence. The 301, 304 angularorientation of the photovoltaic bristles on such corrugated photovoltaiccells 300, 400 ensures that incident sunlight strikes the photovoltaicbristles at angles of incidence that will increase photon absorption.

Various embodiment methods of making photovoltaic bristles are nowpresented.

An embodiment method 800 for manufacturing photovoltaic bristles using apress or stamping process is illustrated in FIGS. 6A-6H, 7A-7C, FIG. 8.This embodiment method 800 may enable fabricating photovoltaic bristlesusing low-cost substrate materials such as plastics and polymers thatmay be processed rapidly in large volumes. This embodiment method willbe described with reference to FIGS. 6A-6H and FIG. 8 together. Althoughthe figures illustrate and the text describes a rod imprint design, avia design may be similarly created as shown and described withreference to method 1600. Additionally, any of a variety of raisedshapes other than cylindrical rods or cones may be produced on thesubstrate using the embodiment methods and embodiment imprintingsystems, including ridges, a mesh of interlocking ridges, hemispheres,etc.

In method 800 in block 804, a plastic or polymer block or startingmaterial may be processed in order to prepare it for a pressing orforming operation. The methods used for preparing such a polymer forpressing will depend upon the type of plastic or polymer selected. Asillustrated in FIGS. 6A and 6B, in block 808 a die or mold 602 includinga number of bristle holes 604 for forming the bristle cores may bepressed into the plastic or polymer material 202 and then removed,thereby forming an array of cores 106 out of the plastic polymer 202. Inan embodiment, vertical stamp 602 moves in a downward vertical mannerinto a polymer substrate 202 forming cores 106 and moving verticallyaway from the substrate 202 and the formed cores 106. Alternatively, arolling press or rolling die may be applied to a moving sheet or tray ofmaterial similar to printing press techniques.

When using a rolling press or rolling die a separate roll-to-web andweb-to-plate sub-process may create the associated rolling stamps andthe array of cores on the substrate for use in method 800. Thesub-process is discussed in depth later in this application withreference to FIGS. 33A-33G, 34, 35A-35E, 36A-36E. Generally, a mastertemplate is created using photolithographic techniques or nanoimprintlithography. The master template imprints a pattern on a polymer sheetor a web. The sheet or web may be a base material with a thin polymerimprintable layer or coating. For example, the sheet could be glassand/or the web could be polyester. The web is then used in combinationwith rollers (e.g., a rolling stamp) to stamp cores on a substratesimilar to substrate 202 with cores 106 illustrated in FIG. 6B.

In block 810, the newly formed array of cores 106 may be cured orotherwise processed in order to improve the material properties, such asto harden the material. This may involve processing with heat,ultraviolet radiation, and/or chemical vapor exposure, as would bewell-known in the polymer arts and depend upon the type of materialused. In an embodiment, the material processing in block 810 may beaccomplished as part of the stamping operation in block 808, either aspart of the stamping operation and as a host stamping process, orentirely as a post-stamping process. For example, a rolling stamp mayinclude an ultraviolet light that is configured so that when the rollingstamp rotates over the unformed substrate 202 the ultraviolet lightsimultaneously cures or partially cures the newly formed cores 106.

As illustrated in FIG. 6C, in block 812, an inner conductive layer 107may be formed over the cores 106. This may be accomplished by chemicalvapor deposition, plasma enhanced chemical vapor deposition, physicaldeposition, plasma deposition, sputtering techniques, orelectro-deposition techniques. The inner conductive layer 107 mayfurther be formed or thickened by electroplating processes. Multipleconductive layers may be applied as part of block 812. In an embodiment,the inner conductive layer or layers may be one or more of copper,aluminum, gold, nickel, titanium, silver, tin, tantalum, and chromium,as well as alloys of such metals. This process forms an inner conductingcore for the photovoltaic bristle.

To form the photovoltaic portion of the photovoltaic bristles, a numberof semiconductor layers may be applied to the inner conducting coreusing well-known semiconductor processing methods. As illustrated inFIG. 6D, in block 804, a first absorber layer of semiconductor materialmay be formed over the inner conductive layer. For example, the firstabsorber layer 105 may include silicon, amorphous silicon,polycrystalline silicon, single crystal silicon, cadmium telluride,cadmium sulfide, gallium arsenide, copper indium selenide, and copperindium gallium selenide. The first absorber layer 105 over the innerconductive layer 107 by electroplating, chemical vapor deposition,atomic layer deposition, etc.

As illustrated in FIG. 6E, in block 842 a second semiconductor materiallayer may be formed over the first absorber layer, with the first andsecond absorber layers having material properties to create a p-njunction or n-p junction configured to release electrons upon absorbinga photon. Any deposition method used to add the first absorber layer 105may also be used to add the second absorber layer 104. In an embodiment,the deposition method for the second absorber layer 104 may be the samedeposition method used for adding the first absorber layer 105. In anembodiment, the second absorber layer 104 may include a semiconductormaterial. For example, the second absorber layer 104 may includesilicon, amorphous silicon, polycrystalline silicon, single crystalsilicon, cadmium telluride, cadmium sulfide, gallium arsenide, copperindium selenide, and copper indium gallium selenide. In an embodiment,the second absorber layer 104 may be an absorber sublayer or regioncomprising the same material as the first absorber layer 105 with adifferent dopant. For example, the first absorber layer 105 may bep-doped amorphous silicon and the second absorber layer 104 may ben-doped amorphous silicon. In an embodiment, the second absorber layer104 may be an absorber sublayer comprising a different material as thefirst absorber layer 105. For example, the first absorber layer 105 maybe p-doped cadmium telluride and the second absorber layer 104 may ben-doped cadmium sulfide. In optional block 846, additional absorberlayers of semiconductor materials may be applied to form multiple p-nand/or n-p junctions (e.g., n-p-n or p-n-p junctions).

With the photon absorber layers formed, an outer conductive layer may beformed in block 848 as illustrated in FIG. 6G. The outer conductivelayer may be a transparent conducting oxide or transparent conductingnitride, as are well-known in the photovoltaic technologies. In anembodiment, the only two absorber layers 104, 105 may be applied, andthus the outer conductive layer 103 is deposited (e.g., by chemicaldeposition or physical deposition) over the last absorber layer 104 asshown in FIG. 6F. In optional block 852, additional outer conductivelayers may be applied depending upon the configuration of thephotovoltaic bristles. Although the outer conductive layer in FIG. 6Gincludes two layers, any number of layers may make up the outerconductive layer 103.

Corrugated photovoltaic cells may also be configured using similarprocesses as illustrated in FIGS. 7A-7C. For example, as illustrated inthese figures, the operations of forming an array of cores in theplastic or polymer in block 808 may be accomplished by alternatelypressing the material 302 with dies that are oriented at the desiredangle of the corrugated surfaces. For example, photovoltaic bristles 106may be formed on corrugated surfaces in the first orientation bypressing the material with dies 702 oriented along one angle asillustrated in FIG. 7B, followed by pressing the opposite surfaces withopposite oriented dies 702 as illustrated in FIG. 7C.

To form the embodiment illustrated in FIG. 4C in which photovoltaicbristles are formed on only alternating sides of the corrugated surface,only a single pressing step as illustrated in FIG. 7B may beaccomplished. In some embodiments, in optional block 854 a reflectivelayer may be applied to the surfaces that do not feature photovoltaicbristles. This may be accomplished using photoelectric graphic methods,such as coding the photovoltaic bristles with a photoresist that isremoved from the other surfaces before a reflective layers applied.

As illustrated in FIG. 6H, in optional block 856 the conductive tracesmay be added to portions of the solar cells to gather and distributeelectricity from the photovoltaic bristles, thereby reducing the pathlength of electrons through the transparent conducting oxide layers.Finally in optional block 858, a transparent coating may be applied overthe bristles in order to provide desirable strength and photonabsorption c characteristics. For example, a transparent coating 608 mayseal each bristle in a transparent material providing stability to eachbristle to prevent the bristles from breaking. The transparent coating608 may be conventional shatterproof material such as ethylene-vinylacetate (EVA).

In a further embodiment method that uses some of the same processes asin method 800, the material forming the cores 106 may be poured andformed in a mold 612 instead of being pressed, as illustrated in FIGS.6I through 6K. As illustrated in FIG. 6I, instead of a die 602, the samebasic shape may be inverted to form a mold 612 onto which may be pouredthe material 614 to form the cores and supporting substrate. Thismaterial 614 may be a plastic or polymer, but may also be othermaterials, such as a metal, a ceramic paste, or a liquid glass (e.g.,common glass). In this embodiment, the operations of forming the arrayof cores in block 808 include pouring the base material 614 into themold 612, sufficiently covering the mold surface to provide a substrate202 as shown in FIG. 6J. The material may be cured in block 810 in thisstate before the mold 612 is removed as shown in FIG. 6K. Thereafter,the operations of depositing absorber layers and outer conductive layersmay be accomplished as described above with reference to blocks 812-858.

Another embodiment method for forming an array of bristles for ametamaterial device involves plating up metal cores usingphotolithographic methods to create a template on a substrate. Theplating up method is illustrated in FIGS. 9A-9J and FIG. 10. In block1008 a metal layer may be deposited over a substrate. As illustrated inFIG. 9A the metal layer 187 may be deposited over the substrate 202 bychemical deposition or physical deposition. In block 1010 a photoresistlayer over the metal layer. The photoresist layer 189 may be depositedover the metal layer 187 by chemical vapor deposition or physicaldeposition as shown in FIG. 9A. The photoresist layer 189 may be apositive photoresist or a negative photoresist.

In block 1012 a mask may be applied over the photoresist. As shown inFIG. 9B, the mask 195 may include holes 195 a through which ultravioletlight may pass so that only the photoresist beneath the holes is exposedas shown in FIG. 9B. In block 1014 the photoresist layer may be exposedto an ultraviolet light through the mask to create exposed photoresistportions 189 a as shown in FIG. 9B. When a positive photoresist is used,the exposed photoresist portions 189 a match the mask holes 195 a.However, if a negative photoresist is used, ultraviolet light may beable to pass through the entire mask except through solid portions ofthe mask which block the ultraviolet light. After the ultraviolet lightis applied to the photoresist 189 creating exposed portions 189 a, themask 195 is removed leaving the entire photoresist layer 189.

In block 1016 the method may include developing the photoresist layer tocreate a template of masked portions. A developer may be used todissolve only the exposed portions of the photoresist. Assuming themethod uses a positive photoresist 189, the exposed photoresist portions189 a are removed creating voids 189 b in the photoresist layer thatextend to the metal layer 187 as shown in FIG. 9C. These voids 189 aalong with the remaining photoresist layer 189 form a template over themetal layer 187.

In block 1018 additional metal may be added to the metal layer throughthe photoresist layer using electroplating, chemical vapor deposition orplasma deposition methods, forming metal cores. As shown in FIG. 9D themetal cores 106 may fill the voids 189 b within the photoresist 189 byelectroplating metal in the voids 189 b. Metal cores may also extendabove the photoresist layer. Alternatively, a second metal layer mayfill the voids 189 b and covers the remaining portions of thephotoresist layer 189 (not shown). The metal cores 106 may be the samematerial as the metal layer 187 such as gold, copper, nickel,molybdenum, iron, aluminum, or silver, or an alloy of the same.

In block 1020 the photoresist layer may be removed using conventionalmethods. As shown in FIGS. 9D and 9E, the metal cores 106 may only fillthe voids 189 b created by the exposed photoresist layer through anelectroplating process. When the photoresist layer 189 is removed, onlythe formed metal cores 106 (within voids 189 b) remain. Alternatively,if a second metal layer fills the voids 189 b and covers the photoresistlayer 189, a lift-off process known in the art may remove thephotoresist layer 189 and the second metal layer leaving only the metalcores 106. The resulting metal cores 106 from the lift-off process mayhave height greater than the voids 189 b.

In block 1040 a first absorber layer (i.e., sublayer) 105 may bedeposited over the metal core 106 for metamaterials 200 illustrated inFIG. 9F. In an embodiment, the first absorber layer 105 may include asemiconductor material. For example, the first absorber layer 105 mayinclude silicon, amorphous silicon, polycrystalline silicon, singlecrystal silicon, cadmium telluride, cadmium sulfide, gallium arsenide,copper indium selenide, and copper indium gallium selenide. In anembodiment, the first absorber layer 105 may be deposited over the metalcore 106 by electroplating, chemical vapor deposition, atomic layerdeposition, etc. In an embodiment, the first absorber layer 105 may bedeposited over the inner conductive layer 107 by sputtering, electronbeam, pulsed laser deposition, etc.

In block 1042 a second absorber layer 104 may be deposited over thefirst absorber layer 105 for metamaterial 200 as illustrated in FIG. 9G.Any deposition method used with respect to the first absorber layer 105may also be used with the second absorber layer 104. In an embodiment,the second absorber layer 104 may include silicon, amorphous silicon,polycrystalline silicon, single crystal silicon, cadmium telluride,cadmium sulfide, gallium arsenide, copper indium selenide, and copperindium gallium selenide. In an embodiment, the second absorber layer 104may be an absorber sublayer or region comprising the same material asthe first absorber layer 105 with a different dopant. For example, thefirst absorber layer 105 may be p-doped amorphous silicon and the secondabsorber layer 104 may be n-doped amorphous silicon. In an embodiment,the second absorber layer 104 may be an absorber sublayer comprising adifferent material as the first absorber layer 105. For example, thefirst absorber layer 105 may be p-doped cadmium telluride and the secondabsorber layer 104 may be n-doped cadmium sulfide.

In some implementation multiple absorber layers may be applied. So inoptional block 1046, one, two or more additional absorber layers may beapplied over the previous layer in a manner similar to the process stepsin blocks 1040 and 1042. As shown in FIG. 9H, in block 1048, an outerconductive layer 103 may be deposited over the last absorber layer(e.g., second absorber layer 104), such as by chemical deposition orphysical deposition.

As illustrated in FIG. 9I, additional outer conductive layers may beapplied in optional block 1052. In an embodiment, the outer conductivelayers may include a transparent non-conductive layer 103 a (e.g., anoptical transparent polymer) and a conductive layer 103 b (e.g., atransparent conducting oxide). Although the outer conductive layer shownin FIG. 9I includes two layers, any number of layers may make up theouter conductive layer 103. The non-conductive layer 103 a illustratedin FIG. 9I may be a conformal layer which may act as a protectivecoating similar to the transparent coating 608 described below. Theconformal non-conductive layer 103 a may be added by dip coating,chemical vapor deposition, physical deposition, and atomic layerdeposition, and evaporation techniques.

In optional block 1056, current conducting traces may be added to themetamaterials 200 and 300. As explained later with reference to FIGS. 23and 25, the current conducting traces may be added by creating atemplate using photolithography and depositing a highly conductivematerial in a selected position from the template. The currentconducting trace may be deposited on the metamaterial by any knowndeposition method such as chemical vapor deposition, physicaldeposition, plating, or ink jet material deposition. The ink jetdeposition methods may utilize piezoelectric ink jets to add silver orother colloidal conductive material to the desired position withoutdamaging the metamaterial.

Alternatively, the current conductive traces may be added by etchingwith laser ablation in combination with a deposition method such as inkjet. Tuned wavelength lasers may etch desired layers by controlling thelaser's wavelength for different layers within the metamaterial. Onceetching is complete, the method may include adding the electricalconnections such as the current conducting traces at the desiredpositions on the metamaterial by chemical vapor deposition, physicaldeposition, plating or inkjet deposition.

As a further alternative, the metamaterial may be etched using ink jettechnology to apply an acid to precise locations followed by applyingthe conductive material using the same technology, or any otherdeposition method known in the art.

Regardless of method used, the current conducting traces may allow forefficient transfer of electricity by adding a lower resistant electricalpath within the metamaterials.

In optional block 1058 a transparent coating may be deposited over thebristles. As illustrated in FIG. 9J, the transparent coating 608 isdifferent from the outer conductive layer 103 and its sublayers 103 aand 103 b. The transparent coating 608 may completely fill the voidsbetween each bristle and extending beyond the height of each bristle. Asshown, the transparent coating 608 may not be conformal, thus leading todeposition methods that use liquid solutions. Accordingly, the method ofdepositing transparent coating 608 may include one or more of thefollowing: immersion coating techniques, spray gel techniques, extrusiontechniques, a spreader bar, photoresist techniques, sol gel techniques,or any other methods known in the art. The transparent coating 608 mayseal each bristle providing stability and preventing them from breaking,as well as insulating each bristle from any heat created by themetamaterial device. Observations and experimentations also indicateenhanced peak power generation as the sun translates across the sky fora metamaterial device with a transparent coating 608 having an index ofrefraction similar to glass (e.g., around 1.5). All of these benefitsmay add enhanced power performance and total power generation of themetamaterial device.

A further method for forming an array of bristles for metamaterial 200includes forming bristles by etching vias in a substrate through aphotolithographic template. The method includes adding an innerconductive layer 107 and a base layer 202 b over the original substrate202 a and in the vias. The method then includes turning the metamaterialdevice over and depositing absorber layers 104, 105, outer conductivelayers 103 a, 103 b and a transparent coating over the inner conductivelayer. This via method is illustrated in FIGS. 11A-11L and FIG. 12.

In block 1210 a photoresist layer may be deposited over the substrate.The photoresist layer 189 may be deposited over the substrate 202 a bychemical vapor deposition or physical deposition as shown in FIG. 11A.Although FIGS. 11B-11D illustrates a positive photoresist, thephotoresist layer 189 may be negative photoresist.

In block 1212 a mask may be deposited over the photoresist layer. Themask 195 may be any suitable mask known in the art. As shown in FIG.12B, the mask 195 may include mask holes 195 a. Alternatively, if usinga negative photoresist, the pores 195 a may be filters for blockingultraviolet light.

In block 1214 the method may include exposing an ultraviolet light tothe photoresist layer through the mask. The ultraviolet light from theultraviolet light source 193 passes through the mask holes 195 a intothe photoresist layer 189 creating exposed portions 189 a of thephotoresist layer as shown in FIG. 11B. The exposed photoresist portions189 a match the mask holes 195 a. However, if a negative photoresist isused, ultraviolet light may be able to pass through the entire maskexcept through filters where at the locations of mask holes 195 a, whichblock the ultraviolet light. Regardless, after the ultraviolet light isapplied to the photoresist layer 189 creating exposed portions 189 a,the mask 195 is removed leaving the entire photoresist 189.

In block 1216 the method may include developing the photoresist layer tocreate a template, such as by using developer to dissolve the exposedportions of the photoresist as shown in FIG. 11C. After dissolving therequired portions of the photoresist layer, the remaining photoresistlayer 189 portions forms a template over the substrate 202 a.

In block 1218 the substrate may be etched through the template creatingvias. Etching may include wet etching or dry etching. Regardless of theetching technique, vias 1103 are formed from within the substrate 202 a.

In block 1220 the photoresist layer may be removed as shown in FIGS.11D-11E, leaving only the original substrate 202 a with formed vias1103. Any process known in the art may remove the photoresist layer 189from the substrate. For example, the photoresist may be removed bystripping or dissolving the remaining portion of the photoresist.

In block 1222 an inner conductive layer may be deposited in the vias. Asshown in FIG. 11F, the inner conductive layer 107 may be deposited as alayer that covers the bottoms and the sides of the vias 1103 as well ascovering the top of the substrate 202 a. Although the method steps donot explicitly show it, the inner conductive layer 107 may includemultiple layers similar to the outer conductive layer 103 laterdescribed with reference to blocks 1248, 1450, and 1452.

As shown in FIG. 11G, in block 1224 the base layer may be deposited overthe inner conductive layer 107. Although the base layer 202 b is aseparate layer than the original substrate 202 a, it may be the samematerial as the original substrate 202 a. Alternatively, the base layer202 b may be a different substance. It should be noted, that althoughFIG. 11G illustrates the base layer 202 b completely fills the vias1103, the base layer 202 b may only partially fill the vias 1103 and maybe deposited similar to the inner conductive layer 107 resulting in anunfilled void and a non-solid core.

In block 1226 the device may be turned over, and the substrate etched inblock 1228. FIG. 11H illustrates the metamaterial device turned over(i.e., flipped 180 degrees) as well as the original substrate etchedaway leaving the inner conductive layer 107 and the base layer 202 b. Awet etching process (i.e., using acid) or a dry etching process mayremove the original substrate 202 a.

In block 1240, a first absorber layer (i.e., sublayer) 105 may bedeposited over the inner conductive layer 107 for metamaterial 200 asillustrated in FIG. 11I. In an embodiment, the first absorber layer 105may include a semiconductor material. For example, the first absorberlayer 105 may include silicon, amorphous silicon, polycrystallinesilicon, single crystal silicon, cadmium telluride, cadmium sulfide,gallium arsenide, copper indium selenide, and copper indium galliumselenide. In an embodiment, the manufacturing system may add the firstabsorber layer 105 over the metal core 106 by electroplating, chemicalvapor deposition, atomic layer deposition, etc. In an embodiment, themanufacturing system may add the first absorber layer 105 over the innerconductive layer 107 by sputtering, electron beam physical deposition,pulsed laser deposition, etc.

In block 1242 a second absorber layer may be deposited over the firstabsorber layer 105 for metamaterial 200 as illustrated in FIG. 11I. Anydeposition method used to deposit the first absorber layer 105 may beused to deposit the second absorber layer 104. In an embodiment, thedeposition method for the second absorber layer 104 may be the samedeposition method used for adding the first absorber layer 105. In anembodiment, the second absorber layer 104 may include a semiconductormaterial. For example, the second absorber layer 104 may includesilicon, amorphous silicon, polycrystalline silicon, single crystalsilicon, cadmium telluride, cadmium sulfide, gallium arsenide, copperindium selenide, and copper indium gallium selenide. In an embodiment,the second absorber layer 104 may be an absorber sublayer or regioncomprising the same material as the first absorber layer 105 with adifferent dopant. For example, the first absorber layer 105 may bep-doped amorphous silicon and the second absorber layer 104 may ben-doped amorphous silicon. In an embodiment, the second absorber layer104 may be an absorber sublayer comprising a different material as thefirst absorber layer 105. For example, the first absorber layer 105 maybe p-doped cadmium telluride and the second absorber layer 104 may ben-doped cadmium sulfide.

As mentioned above, in some implementations multiple absorber layers maybe applied, so in optional block 1246 such additional absorber layersmay be over the previous layer in a manner similar to the process stepsin blocks 1240 and 1242. As shown in FIG. 11J, in block 1248, an outerconductive layer 103 may be deposited over the last absorber layer(e.g., second absorber layer 104). In optional block 1252, multipleouter conductive layers may be applied as illustrated in FIG. 11K. Asdiscussed above, such outer conductive layers may be applied usingchemical deposition or physical deposition.

In optional block 1256, current conducting traces may be deposited onthe metamaterials 200. As explained later with reference to FIGS. 23 and25, the current conducting traces may be added by creating a templateusing photolithography and depositing a highly conductive material in aselected position from the template. The current conducting traces maybe deposited on the metamaterial by any known deposition method such aschemical vapor deposition, physical deposition, plating, or ink jetmaterial deposition. The ink jet deposition may utilize piezoelectrictechnology and add silver or any other colloidal material to the desiredposition without damaging the metamaterial. Alternatively, the currentconductive traces may be added by etching with laser ablation incombination with a deposition method such as ink jet techniques. Tunedwavelength lasers may etch desired layers by controlling the laser'swavelength for different layers within the metamaterial. Once etching iscomplete, the method may include adding the electrical connections suchas the current conducting traces at the desired positions on themetamaterial by chemical vapor deposition, physical deposition, platingor inkjet deposition. As a further alternative, the metamaterial may beetched by ink jet technology using acid followed by deposition ofconductive material using the same technology or any other depositionmethod known in the art. Regardless of method used, the currentconducting traces may allow for efficient transfer of electricity byadding a lower resistant electrical path within the metamaterials.

As illustrated in FIG. 11L, in optional block 1258 a transparent coatingmay be applied over the bristles. Such a transparent coating 608 may bedifferent from the outer conductive layer 103 and any sublayers 103 aand 103 b. The transparent coating 608 may fully fill the voids betweeneach bristle and extend beyond the height of each bristle. As shown, thetransparent coating 608 may not be conformal thus leading to depositionmethods that use liquid solutions. Thus, the method of depositingtransparent coating 608 may include using one or more of the followingimmersion coating, spray gel techniques, extrusion techniques, aspreader bar, photoresist techniques, sol gel techniques, or any othermethods known in the art. In an embodiment, the transparent coating 608may be a shatterproof material such as EVA. The transparent coating 608may seal each bristle providing stability and to prevent them frombreaking as well as insulate each bristle from any heat created by themetamaterial device. Observations and experimentations also indicateenhanced peak power generation as the sun translates across the sky fora metamaterial device with a transparent coating 608 having a index ofrefraction similar to glass (e.g., around 1.5). All these benefits mayadd enhanced power performance and total power generation of themetamaterial device.

A further method for forming an array of bristles for a metamaterial 200includes forming the bristles by etching vias in a substrate through aphotolithographic template. Bristles are formed within the vias bydepositing an outer conductive layer, absorber layers, an innerconductive layer, an optional base layer. After forming the bristles,the metamaterial may be turned over where the original substrate is leftintact serving as a protective coating and an optical enhancement forthe metamaterial 200. This via method is illustrated in FIGS. 13A-13Land FIG. 14. As shown in FIG. 13A-13L and the method steps in FIG. 14,an etching technique may be used to create vias, which is particularlyuseful when using a glass substrate.

In block 1410 a photoresist may be deposited over the substrate. Thephotoresist layer 189 may be deposited over the substrate 202 a by spinon, spray on, or other controlled flow methods know in the art as shownin FIG. 13A. Although FIGS. 13B-13D illustrate a positive photoresist,the photoresist layer 189 may be negative photoresist.

In block 1412 a mask may be positioned over the photoresist layer. Themask 195 may be any suitable mask known in the art. As shown in FIG.12B, the mask 195 may include mask holes 195 a. Alternatively, if usinga negative photoresist, the pores 195 a may be filters for blockingultraviolet light.

In block 1414 the method may include exposing an ultraviolet light tothe photoresist layer through the mask. The mask 195 may be any suitablemask known in the art. As shown in FIG. 13B, the mask 195 may includemask holes 195 a.

In block 1416 the method may include developing the photoresist layer todissolve the exposed portions of the photoresist layer. Assuming apositive photoresist layer 189, the exposed portions 189 a are removedcreating voids 189 b in the photoresist layer that extend to thesubstrate 202 a as shown in FIG. 13C. After dissolving the requiredportions of the photoresist layer 189, the remaining photoresist layer189 forms a template over the substrate 192.

In block 1418 the substrate may be etched through the template creatingvias. Etching may include wet etching or dry etching. Regardless of theetching technique employed, vias 1103 are formed from within thesubstrate 192.

In block 1420 the photoresist layer may be removed leaving the substrate192 with formed vias 1103 as shown in FIGS. 13D-13E.

Since the outside layers of the photovoltaic bristles are laid downfirst, conductive traces used to draw current from the photovoltaiccells may be laid down as a first step. Thus, in optional block 1421,conductive traces may be applied to the substrate. Vias for suchconductive traces may be formed as part of the operations in blocks1410-1420. Alternatively, conductive traces may be applied to thesubstrate using dedicated photolithography steps, laser ablation steps,and deposition steps such as those described above and below. In aparticular embodiment, the conductive traces may be applied using sprayjet techniques. In block 1422 an outer conductive layer may be depositedin the vias, such as by chemical vapor deposition or physicaldeposition. If conductive traces are prior to the outer conductivelayer, the method may include depositing the outer conductive layer 103over the conductive traces as a conformal film.

Although not shown in FIGS. 13A-13L, the metamaterial may include anouter conductive layer 103 with multiple sublayers. So, in optionalblock 1452 another outer conductive layer may be applied over theprevious layer, essentially repeating blocks 1450 and 1452. As shown inFIGS. 13G-13H, in block 1440 a first absorber layer may be deposited onthe outer conductive layer(s), and in block 1442 a second absorber layermay be deposited over the first absorber layer. The first and secondabsorber layer 104, 105 may be applied by chemical vapor deposition.

In block 1446 additional absorber layer applied over the previous layerin a manner similar to the process steps in blocks 1440 and 1442. Inblock 1448, an inner conductive layer 107 may be applied over the lastabsorber layer (e.g., second absorber layer 105). In an embodiment, themethod may include adding only two absorber layers 104, 105 and thus theinner conductive layer 107 is deposited over the last absorber layer 105by chemical deposition or physical deposition as shown in FIG. 13I.Although the method steps do not explicitly show it, the innerconductive layer 107 may also include multiple layers similar to theouter conductive layer 103.

In block 1424 a base layer may be deposited. As shown in FIG. 13J, thebase layer 202 may be different from the substrate 192 associated withblock 1410. The base layer 202 may be deposited over the innerconductive layer 107 and serves as the actual bottom substrate of themetamaterial device once the vias are turned over. The base layer 202may fill the vias 1103 creating bristles with solid cores.Alternatively, as shown in FIG. 13J, the base layer 202 may not fill thevias 1103, creating bristles with non-solid cores. Regardless, the baselayer 202 may be deposited over the inner conductive layer 107 by anymethod known in the art.

In block 1426 the metamaterial may be turned over as shown in FIG. 13K,so that the bristles are turned upright presenting the originalsubstrate 192 covering the outer conductive layer 103 at the top and thebase layer 202 at the bottom of the device. In optional block 1460 thesubstrate may be further processed, such as to form an antireflectionlayer or rough outer surface 192 a as shown in FIG. 13L.

In an alternative embodiment method, lasers 2401 may create vias 1103out of a substrate or index matched material as illustrated in FIGS. 13Mthrough 13O. The lasers 2401 may be controlled in terms of exposure timeand energy in order to control the depth and size of the vias. Aftercreating the vias 1103, the method 1400 operations described above withreferences to blocks 1421, 1448, 1452, 1440, 1442, 1446, 1442, 1422,1424, 1426, 1458, and 1460 may be followed.

Stamps may create vias out of a substrate such as a transparent polymer.When using a polymer, a UV source may cure the stamped vias creating amore rigid structure followed by adding conductive layers, absorberlayers, and a base layer. The stamping via method for forming an arrayof bristles for a metamaterial device is illustrated in FIGS. 15A-15Jand FIG. 16.

In block 1608 an array of vias may be formed out of the processedpolymer. As illustrated in FIGS. 15A-15B, a stamping process may be usedto create vias 1103 out of a polymer substrate 192. In block 1610 theformed polymer may be cured or otherwise treated to yield desiredmaterial properties. For example, such curing/treating may includeheating and/or exposure to an ultraviolet light source 193.

The stamping process may include a rolling press or rolling die tocreate vias 1103 on a substrate 192 similar to FIG. 15B. When using arolling press or a rolling die, a roll-to-web and a web-to-platesub-process may create the associated stamps and vias method 1600. Therolling press or rolling die sub-process is described in more detailbelow with reference to FIGS. 33A-33G, 34, 35A-35E, 36A-36E.

Similar to method 1400, the method 1600 includes laying down the outsidelayers of the photovoltaic bristles are laid down first, so conductivetraces used to draw current from the photovoltaic cells may be laid downprior to the outer conductive layer 103. Thus, in optional block 1612,conductive traces may be applied to the substrate. Vias for suchconductive traces may be formed as part of the operations in blocks1608-1610. Alternatively, conductive traces may be applied to thesubstrate using dedicated photolithography steps, laser ablation steps,and deposition steps such as those described above and below. Inparticular embodiment, the method may include applying conductive tracesusing a spray jet techniques. In block 1622 an outer conductive layermay be deposited in the vias. If conductive traces are added prior tothe outer conductive layer 103, the method may include depositing theouter conductive layer 103 over the conductive traces as a conformalfilm. As illustrated in FIG. 15D, the outer conductive layer 103 may bedeposited over the polymer 192 and in the vias 1103.

Although it is not shown in FIGS. 15A-15J, multiple outer conductivelayers 103 or sublayers may be applied. So, in optional block 1652additional outer conductive layers may be applied over the previouslayer.

As shown in FIGS. 15E-15F, in block 1640 a first absorber layer may beapplied over the outer conductive layer(s), and in block 1642 a secondabsorber layer may be deposited over the first absorber layer. Themethod may deposit the first and second absorber layer 104, 105 bychemical vapor deposition. In optional block 1646 additional absorberlayers may be deposited over the other absorber layers in a mannersimilar to the process steps in blocks 1640 and 1642.

As shown in FIG. 15G, in block 1648, an inner conductive layer 107 maybe applied over the last absorber layer (e.g., second absorber layer105), such as by chemical vapor deposition or physical deposition. Theinner conductive layer 107 may also include multiple layers similar tothe outer conductive layer 103 earlier described with reference toblocks 1622, 1650, and 1652.

As shown in FIG. 15H, in optional block 1624 a base layer may beapplied. The base layer 202 may be different from the polymer 192applied in block 1608 because the base layer 202 is deposited over theinner conductive layer 107 and serves as the actual bottom substrate ofthe metamaterial device once turned over. Although the polymer 192 maybe of the same material as the base layer 202, the polymer 192 may serveas an outer transparent coating to the metamaterial device once themetamaterial is complete. The base layer 202 may fill the vias 1103creating bristles with solid cores. Alternatively, as shown in FIG. 15J,the base layer 202 may not fill the vias 1103, creating bristles withnon-solid cores. Regardless, the base layer 202 may be deposited overthe inner conductive layer 107 by any method known in the art.

As shown in FIG. 15I, in block 1626 the metamaterial may be turned overfor further processing. In optional block 1660 the substrate 192 may beprocessed to give it desired physical properties, such as hardening orpolishing. The processing may include forming an antireflection layer orrough outer surface 192 a as shown in FIG. 15J.

In a further embodiment method that uses some of the same processes asin method 1600, material 1112 in which vias 1103 are poured into a mold1110 instead of being pressed, as illustrated in FIGS. 15K through 15M.As illustrated in FIG. 15K, instead of a die, the same basic shape maybe inverted to form a mold 1110 onto which may be poured the material1112 to form the vias 1103 and supporting substrate. This material 1113may be a transparent plastic, polymer or glass that will ultimately havethe desired optical properties in the finished product. In thisembodiment, the operations of forming the array of vias 1103 in block1608 include pouring the base material 1112 into the mold 1110,sufficiently covering the mold surface to provide a substrate 1112 asshown in FIG. 15L. The material may be cured in block 1610 in this statebefore the mold 1110 is removed as shown in FIG. 15M. Thereafter, theoperations of depositing outer conductive layers, absorber layers andinner conductors may be accomplished as described above with referenceto blocks 1612-1626.

As a further alternative embodiment, vias may be formed by adding anindex-matched nano-imprinted layer over a substrate. The nano-imprintedlayer includes the vias for methods 1200, 1400, 1600 and may usesuitable nano-imprinting techniques known in the art. For example,methods 1200, 1400, and 1600 may include depositing a nano-imprintedlayer material with an index of refraction of 1.5 over a glass orpolymer substrate.

As mentioned with reference to block 808 of FIG. 8 forming an array ofcores out of the processed polymer may include using a rolling die orrolling press. Similarly, with reference to block 1608 of FIG. 16,forming an array of vias may also include using a rolling die or rollingpress. Although a rolling press may be directly applied to a substrateor a moldable layer on top of the substrate, using such a method maydamage a master template having a particular pattern for creating thecores or vias. Thus, to increase yield and throughput of creatingsubstrates with an array of cores or vias, a master template may be usedto create daughter templates on a web, and each daughter template webmay be applied to a substrate to create the desired core or via patternin a surface material that will be subsequently processed to form thesolar arrays. For example, a master template including cores may imprintvias on a substrate applied to a web creating a daughter template. Thedaughter template with vias may then be applied to a substrate to createcores on the substrate. After curing to increase material strength ofthe newly formed cores, the substrate may be further processed usingembodiment methods such as described above with reference to FIG. 8 andblocks 810-858. As an alternative example, a master template includingvias may be applied to a substrate on a web to create a daughtertemplate featuring rods that may then be applied to a substrate toimprint vias into the substrate (or a layer over a substrate). The viaimprinted substrate may be further processed using embodiment methodssuch as described above with reference to FIG. 16 and blocks 1612-1660.

An embodiment method 3400 for manufacturing an array of cores forphotovoltaic bristles using a rolling press or die is illustrated inFIGS. 33A-33G and FIG. 34. Using a rolling press or die method asdescribed below may enable processing methods that reduce the number ofdefects in fabricating photovoltaic bristles by creating reusable mastertemplates and daughter dies that may be inspected with inspectionresults used in a feedback control system to bypass imperfect portions.

Referring to FIGS. 33A-33G and FIG. 34 together, in block 3402 of method3400 an original master may be created to form a patterned array ofbristles for the metamaterial device. Stamping processes such asnano-imprint lithography may create the original master 3306 with rods3308 from a flexible material as illustrated in FIGS. 33A and 33B. Anyknown process in the relevant art may be used to create such mastertemplates. Companies such as EVG, Obducat, NIL Technology, Nanoex,Molecular Imprints, and Süss Microtech work with nanoimprint lithographyand have refined reliable nanoprint lithography techniques. As analternative, traditional photolithography also may create the originalmaster.

If using nanoimprint lithography, the process may include imprinting thedesired pattern onto the original master 3306 created out of a flexiblematerial such as a polymer or polydimethylsiloxane (PDMS). In optionalblock 3404 a suitable metal, such as nickel, may be electroformed overthe original master to create a rigid master template or shim. Suchmetal plating may also be applied after the master is formed into oronto a roller as described below with reference to block 3408. The rigidmaster template may be used to create flexible master templates such asthe master webs described below. Whether created by the rigid mastertemplate or formed as the original master, flexible templates such asPDMS may be used to imprint patterns on more rigid materials.

The master template may be formed in one piece, or a large mastertemplate may be formed from stitching together the master template inblock 3406. Whether the master template is flexible or rigid, multiplemasters may be stitched together as illustrated in FIG. 33C. Once thelarge master template is formed, in block 3408, the large mastertemplate may be wrapped around a drum roller (or formed into a roller)as illustrated in FIG. 33D. The drum roller may then be used forsubsequent processing in a roll-to-web system as described below.

The web material may be a polymer or polyester film, such a Dupont'sMylar®. By way of example, the web material may have a thickness of 25to 250 microns, a length of 100 to 2000 feet, and a width of 0.5 to 6feet. In block 3410 a first moldable material, such as a lacquer,spin-on-glass coatings, a sol-gel, or PDMS, may be applied to a web tocoat a thin layer of the material over the web. Since the web itself isflexible, a flexible material such as PDMS may be less restricting thansol-gel, spin-on-glass coatings when moving through the rollers andsubsequent processing.

In block 3412 the first pattern from the large master template may beimprinted to the coated web to create a second imprint pattern on theweb as illustrated in FIG. 33E. In this process operation, the drumroller with a rod pattern imprints vias 3314 b into the coated materialon the web by pressing the web and the coated material against atransfer spacing roller 3318. Alternatively, the drum roller with a viapattern creates a rod pattern from the coated material on the web (notshown). In block 3414 the second imprint pattern on the web may be curedor otherwise processed to increase its material strength. An ultraviolet light or a thermal mechanism for applying heat may be used tocure the second imprinted pattern. If using PDMS as a moldable material,a thermal mechanism may apply heat to cure the imprinted pattern. Theresult of these processor operations is a daughter die web suitable foruse in subsequent operations for creating a substrate with cores (oralternatively vias) on a substrate that will eventually become solarcells. As an alternative embodiment method, the web itself may be aflexible substrate and with a cured second imprinted pattern the websubstrate may be suitable for use in embodiment methods (e.g., method800 or 1600) describe herein to create metamaterial devices.

In block 3416 the master web may be installed on rollers in aweb-to-plate process. In block 3418 a moldable material may be appliedto a substrate or surface on which the solar arrays will be formed. Forexample, the moldable material may be a polymer that may be cured (e.g.,by exposing it to ultra violet radiation) after it is applied to asubstrate or support surface and imprinted as described below. Asanother example, the moldable material may be a flexible thermallycurable sol-gel that is applied to a substrate or support surface andimprinted as described below. Alternatively, the substrate itself may bea moldable material and thus the operations in block 3418 may involvecreating the substrate of moldable material.

As illustrated in FIG. 33F, the second pattern from the master web maybe imprinted on the moldable material to create a third imprint patternon or in the substrate in block 3420. In the example illustrated in FIG.33F, a daughter die web with vias 3314 b will form cores 3320 a of themoldable material 3320 on the substrate 3322. As described below, theprocess pressing the daughter die 3316 into the moldable material 3320on the substrate 3322 may be controlled so that the two surfaces cometogether without sliding, which could deform or fail to form the desiredcores 3320 a (or vias).

In block 3422 the cores 3320 a (which are the third imprinted pattern)illustrated in FIG. 33G or vias (not shown) may be cured or otherwiseprocessed to increase their strength and rigidity before subsequentprocessing according to embodiment methods described above withreference to FIGS. 8 and 16. As mentioned above, such curing orprocessing of the cores or vias may involve exposure to ultra violetlight (e.g., to increase cross linking in a polymer material) or heating(e.g., to convert sol gel into a glass or ceramic).

FIG. 35A illustrates an embodiment roll-to-web system 3500 suitable foruse in the operations described above with reference to blocks 3406-3414in method 3400. The illustration of the roll-to-web system 3500 in FIG.35A and the following description is provided as an illustrative exampleand is not intended to limit the scope of the claims as otherroll-to-web system configurations (e.g., different rollerconfigurations, different web paths and different sequences ofoperations) are possible without departing from the scope of the presentinvention.

In the embodiment roll-to-web system 3500 illustrated in FIG. 35A, a webmaterial may pass through a series of rollers configured and controlledto maintain tension and orientation, apply a moldable material to theweb, and imprint a first pattern from a master die on the moldablematerial to create a second pattern of cores or vias in the moldablematerial. That second pattern of cores or vias in the moldable materialmay be subsequently cured/processed to form the daughter die on the web.

The roll-to-web system 3500 may include an unwind roller 3502 that maybe driven by an unwind motor 3502 a connected to an unwind motorcontroller 3502 b to control the rotation of the unwind roller. Anuncoated web 3501 a may be installed on the unwind roller 3502 and beunwound throughout the roll-to-web system 3500. From the unwound roller3502, the uncoated web 3501 a may roll over a tension sensor 3312. Thetension sensor may provide web-tension information to the unwind motorcontroller 3502 b which may use this information as feedback along withtorque sensing feedback from the unwind motor 3502 a to control webtension through the roll-to-web system 3500.

The uncoated web 3501 a may travel over a tracking roller 3504, whichmay be adjusted by the control system to control the lateral position ofthe web in the system in response to signals from an edge sensor 3505.By adjusting the tracking roller 3504, the web's position on the rollersmay also be adjusted to an optimum position/orientation to preventskewing of the pattern on the web. For example, if the web is too far tothe left side of the rollers, the tracking roller may be adjusted tomove the web back toward the center of the rollers.

The uncoated web 3501 a may travel through S-wrap rollers 3506, whichcontrol the velocity and tension of the web 3501 as it passes throughthe roll-to-web system 3500. The S-wrap rollers 3506 may adjust thevelocity of the web 3501 traveling through the roll-to-web system 3500based on data from drum roller speed encoders 3521. In this manner, theS-wrap rollers may serve to synchronize the speed of the web as it meetswith the drum roller (which includes the master die) that imprints thepattern on the web 3501. Closely controlling the relative speed of theweb and the drum roller reduces the chance for defects to be printed onthe daughter dies as well as the chance for damaging the master die onthe drum roller.

The uncoated web 3501 a may travel between a transfer roller 3507 and arubber roller 3508. The transfer roller 3507 picks up a layer ofmoldable material 3509 and applies the layer to the web, while a shearroller 3510 ensures the applied layer is of the desired thickness. Asthe uncoated web 3501 a travels between the rubber roller 3508 and thetransfer roller 3507, the transfer roller 3507 collects the moldablematerial 3509 on the transfer roller 3507. Prior to the transfer roller3507 applying the first moldable material 3509 to the uncoated web 3501a, the shear roller 3510 removes excess moldable material 3509 from thetransfer roller 3507 to ensure a consistent coating on the web 3501 a. Arubber roller 3508, potentially made of high durometer ground rubber,may provide support to the web 3501 while the transfer roller 3507applies the first moldable material 3509.

After the transfer roller 3507 applies the first moldable material 3509to the uncoated web 3501 a, a thickness sensor 3511 may measure thethickness of the first moldable material 3509 on the coated web 3501 b.The thickness sensor may be used by a control system that may send asignal to cause the shear roller 3510 shift position in order tomaintain a consistent thickness and compensate for any thicknessvariations in the uncoated web 3501 a. For example, if the thicknesssensor indicates that the coated web's thickness is higher than a setpoint, the control system may cause the shear roller 3510 to move closerto the transfer roller 3507, thereby removing more of moldable material3509 from the transfer roller 3507 prior to its application to theuncoated web 3501 a.

The coated web 3501 b passes between the drum roller 3512, whichincludes the master template, and a transfer spacing roller 3513 inorder to imprint the daughter die pattern in the moldable material oncoated web 3501 b. The moldable material on the coated web 3501 baccepts the first pattern as the coated web 3501 b is pressed againstthe drum roller 3512 to create a second pattern in the moldable material3509. The speed of rotation of the drum roller 3512 is closelycontrolled by a control system so that it spins in conformity with thespeed of the moving web 3501 to precisely imprint the first pattern onthe web. To do so, the control system may receive signals from speedencoders 3521 coupled to the S-wrap roller(s) 3506 and use thisinformation in a closed-loop control algorithm to ensure that thesurface of the drum roller matches the speed of the web 3501 passingbeneath or over it. Depending on the type of moldable material, theimprinted web 3501 c may be cured/processed (e.g., thermally or withultra violet light) by a curing mechanism 3514.

The cured web 3501 d may travel over a support roller 3515 and a secondtension sensor 3516 prior to being collected on a wind roller 3518. Thewind roller 3518 may be driven by a wind motor 3518 a controlled by awind motor controller 3518 b. The wind motor controller 3518 b mayadjust the wind up speed of the wind roller 3518 based on the torque ofthe wind motor 3518 a and signals from the second tension sensor 3516 toassist in maintaining proper web tension and a speed of advance.

The roll-to-web system 3500 may also include an inspection camera 3519that may scan the cured web 3501 d for defects. Images from theinspection camera 3519 may be processed by a computer to identify areasof defects, which may be recorded against position on the web in aweb-mapping database 3520 that may be used in controlling the finalprinting process. As described below, a web-to-plate system 3600 mayaccess the web-mapping database 3520 and adjust its system parameters(e.g., web speed, substrate linear speed, sheet gap mechanism) to avoidapplying any mapped defects in the web 3501 d to substrate beingprocessed in such a system.

The roll-to-web system may also include a moldable material processingsystem 3522. The moldable material processing system 3522 may be fluidlyconnected to a moldable material container that houses the moldablematerial 3509 for the transfer roller 3507. The moldable materialprocessing system 3522 may recirculate the moldable material 3507through system components (filters, heat exchangers, etc) to ensure themoldable material 3507 is clean and at the proper temperature forapplying to the web 3501 a. The moldable material processing system 3522may add moldable material 3509 as needed to ensure ample moldablematerial for the roll-to-web system 3500.

Various portions of the roll-to-web system 3500 may be subject tohumidity and temperature controlled to ensure that the moldable material3509 adheres to the web 3501 and that the moldable material 3509 acceptsthe desired pattern from the drum roller 3512 with minimal defects. Thismay be especially important if the moldable material 3509 is a sol-gelor other thermally cured material.

FIGS. 35B-35E illustrate example control systems that may be used tocontrol various portions and components of the roll-to-web system 3500described above enable high precision printing from the drum roller 3512to the web 3501. FIG. 35B illustrates the electrical controls betweenthe tension sensor 3503, the unwind motor 3502 a, and the unwind motorcontroller 3502 b. The unwind motor controller 3502 b may utilize a PIDcontroller system that adjusts the unwind motor 3502 a based on inputsfrom the tension sensor 3503, a tension sensor set point, a torque inputfrom the unwind motor 3502 a, and a torque set point. A skew actuatorcontroller 3504 a illustrated in FIG. 35C may adjust the position of thetracking roller 3504 based on data from the edge sensor 3505 and a setpoint. An S-wrap motor controller 3506 a illustrated in FIG. 35D maycontrol speed of the s-wrap rollers 3506 and the corresponding webvelocity through the roll-to-web system. The S-wrap motor controller3506 a controls S-wrap rollers 3506 to synchronize the web velocity withthe drum roller's rotational speed based on data from the speed encoder3521 and a set point. The wind motor controller 3518 b illustrated inFIG. 35E is similar to the unwind motor controller 3502 b illustrated inFIG. 35B, except that the wind motor controller 3518 b accepts inputdata based on the second tension sensor 3516, a tension set point,torque data from the wind control motor 3518 a, and a torque set point.

FIG. 36A illustrates an embodiment web-to-plate system 3600 that may besuitable for forming the desired pattern of cores or vias on thesubstrate as described above with reference to blocks 3416-3422 inmethod 3400. The illustration of the web-to-plate system 3600 in FIG.36A and the following description is provided as an illustrative exampleand is not intended to limit the scope of the claims as otherweb-to-plate system configurations (e.g., different rollerconfigurations, different web paths and different sequences ofoperations) are possible without departing from the scope of the presentinvention.

The web-to-plate system 3600 may process a substrate that moves throughthe system on a linear drive mechanism by applying a moldable materialto the surface of the substrate. As an alternative, if the substrate isthe second moldable material, then a moldable material does not need beadded to the substrate. The moldable material applied to the substratein this process may be different from the moldable material that isapplied to the web and used to form the daughter die pattern. Theweb-to-plate system 3600 also passes the daughter die web (which has thesecond template pattern as described above) through a series of rollersthat control its tension and speed of advance, and presses it onto themoldable material on the substrate to create a third pattern, which isthe desired cores or vias. The web-to-plate system 3600 has a websubsection and a plate subsection.

The web subsection will be discussed first. The web-to-plate system 3600may also include a module or apparatus that cures/processes the thirdpattern in order to produce the substrate with a pattern of cores orvias suitable for the embodiment processes described above withreference to FIGS. 8 and 16 for applying photovoltaic materials.

The web 3501 d on the web-to-plate system 3600 is weaved through variousrollers to control tension and position, similar to the roll-to-websystem 3500. The web-to-plate system 3600 may include an unwind roller3602 driven/controlled by an unwind motor 3602 a connected to an unwindmotor controller 3602 b configured to control the rotation of the unwindroller 3602. The daughter die web 3501 d from the roll-to-web processdescribed above may be installed on the unwind roller 3602. The daughterdie web 3501 d may travel across a tracking roller 3603 and an edgeguide sensor 3604. The edge guide sensor 3604 may collect informationregarding the position of the web 3501 d on the rollers relative to aset point, and send that data to a controller of the tracking roller3603. The controller of the tracking roller may use the data to adjustthe position/orientation of the tracking roller 3603 in order to correctthe orientation of the daughter die web 3501 d in the system and preventweb skewing within the rollers.

The web-to-plate system 3600 may include a tension sensor 3606 thatprovides data to an unwind motor controller 3602 b to enable the unwindmotor controller 3602 b to control the unwind motor 3602 a to adjust thespeed of the unwind roller 3606 based on tension data. The unwind motorcontroller 3602 b may also use torque data from the unwind motor 3602 a.Unlike the roll-to-web system 3500, in the web-to plate system 3600 thesame tension sensor 3606 may also be connected to the wind motorcontroller 3608 to enable the wind motor controller 3608 b to controlthe wind motor 3608 a to adjust the speed of the wind roller 3608 basedon the same tension data. The tension sensor 3606 may be positionedafter the velocity roller 3605.

The web-to-plate system 3600 may not include S-wrap rollers to controlthe velocity of the web. Instead, the web-to-plate system 3600 may use avelocity roller 3605 to perform a similar function. The velocity roller3605 may be connected to a velocity roller motor controller 3605 a,which may adjust the velocity of the daughter die web 3501 d to matchthe linear speed of the substrate based on data acquired from the lineardrive controller 3601 a. The velocity roller controller 3605 a may alsoadjust the speed of the web 3501 d based on web-mapping data from theweb-mapping database 3520. For example, if there is a defect in thedaughter die web, the velocity roller 3605 may increase the velocity ofthe daughter die web 3601 d at a certain point in time to ensure thatthe defected portions are not imprinted on the substrate 3609 a.Alternatively or additionally, the linear drive controller 3601 a may becontrolled to pause the advance of the substrates in order to enable aportion of the daughter die web with a defect to be advanced beforeimprinting of the next substrate begins.

The daughter die web 3501 b may travel around the velocity roller 3605past the tension sensor 3606 to a transfer gap roller 3607. The transfergap roller may aid in pressing the daughter die web 3501 d against thesubstrate to imprint the second pattern into moldable material on thesubstrate 3609 a thereby creating the third pattern of cores or vias.Once the daughter die web 3501 d imprints the second pattern on thesubstrate 3609 a, the daughter die web 3501 d may be wound around thewind roller 3608 and used for future processing.

The plate subsection of the web-to-plate system 3600 includes a lineardrive mechanism 3610 configured to control the linear motion and linearvelocity of the substrate 3609 through the web-to-plate system 3600. Thelinear drive mechanism 3610 is connected to a linear drive controller3610 a, which may control the speed of the substrate 3609 in theweb-to-plate system 3600 based on data from the sheet gap controller3611 a, the web-mapping database 3520, and the velocity roller motorcontroller 3605 a.

While the pre-imprinting substrate 3609 a is traveling across the lineardrive mechanism 3610, the sheet gap mechanism 3611 may stop thepre-imprinting substrate 3609 a by a vertical actuation synchronizedwith the movement of the substrate 3609 and the daughter die web 3501 dto reduce imprinting defects. For example, the sheet gap controller 3611a may receive web-mapping data regarding a known defect on the daughterdie web's pattern from the web-mapping database 3520, and in responsecontrol the sheet gap mechanism 3611 to stop the substrate 3609 a frommoving forward in the system when a defective portion of the daughterdie web is present on or near the transfer gap roller 3607 to avoidprinting a defect from the daughter die web 3501 d on to the substrate3609 a. As another example, the sheet gap mechanism 3611 may prevent thesubstrate 3609 a from moving to the second moldable material applicator3612, while the moldable material application is adjusted, refilled,etc. When the sheet gap mechanism is actuated, a sheet gap sensor ortrigger may act as an input to other controllers in the system.

After passing the sheet gap mechanism 3611, a moldable materialapplicator 3612 may apply the moldable material 3613 over the substrateto create a coated substrate 3609 b. A thickness sensor 3614 may detectthe thickness of the moldable material on the coated substrate 3609 band provide feedback to the moldable material applicator 3612 foradjusting the amount of moldable material applied to the substrate 3609a. The coated substrate 3609 b contacts the daughter die web 3501 d withpressure applied by the transfer gap roller 3607 so that the secondpattern from the daughter die web 3501 d is imprinted on the coatedsubstrate 3609 b to create an imprinted substrate 3609 c.

Depending on the type of moldable material, the imprinted substrate 3609c may be cured or processed in a curing mechanism 3615 to increase itsmaterial strength, such as via thermal and/or ultraviolet radiationcuring. After curing, the final substrate 3609 d is ready for furtherphotovoltaic processing according to an embodiment method describedabove with reference to FIG. 8 or FIG. 16. Further processing mayinclude adding absorber layers, inner conductive layers, outerconductive, microtraces, etc.

FIGS. 36B-36E illustrate control systems that may be configured toenable high precision printing from the web to the substrate in theweb-to-plate system 3600. FIG. 36B illustrates electrical controlsbetween the tension sensor 3606, the unwind roller motor 3602 a, and theunwind motor controller 3602 b. The unwind motor controller 3502 b mayutilize a PID controller system that adjusts the unwind motor 3602 abased on inputs from the tension sensor 3606, a tension sensor setpoint, a torque input from the unwind motor 3602 a, and a torque setpoint. The tension input may be used as the lowest level input variableand torque from the unwind motor 3602 a and the wind motor 3608 a may bethe major control variables. The unwind and wind motor controllers 3602b and 3608 b, respectively, will look for a minimum value from thetension sensor 3606 to insure the web has tension. The differentialbetween the wind/unwind torque and a respective set point may be used todetermine dynamic wind or unwind force to be applied in order tomaintain a desired tension. The wind and unwind controller 3602 b and3608 b will evaluate the differential between the two motor systems tocontrol the web tension. Software may run linear and non-linearproportional loop equations based on an input factor. The integralportion will smooth the interactions and the integral sample rate withina sample window. Due to the sensitive nature of the process and the timeconstants involved, the derivative portion may act as a dampener.Similar logic may be applied to the control of the roll-to-web system3500. Further details regarding PID logic and control loops may be foundin U.S. Pat. No. 4,500,408, entitled Apparatus for and Method ofControlling Sputter Coating.

A skew actuator controller 3603 a illustrated in FIG. 36C may adjust theposition of the tracking roller 3603 based on data from the edge sensor3604 and a set point. A velocity controller 3605 a may control the speedof the velocity roller 3605 and the corresponding web velocity throughthe web-to-plate system 3600 as illustrated in FIG. 36D. The velocitymotor controller 3605 a may control the velocity roller 3605 tosynchronize the web velocity with the linear drive speed controlled bythe linear drive controller 3610 a. The wind motor controller 3608 billustrated in FIG. 36E is similar to the unwind motor controller 3602 bof FIG. 36B, except that the wind motor controller 3518 a may acceptinput data based on torque data from the wind control motor 3518 a, anda torque set point.

FIGS. 17-21 illustrate multiple embodiment metamaterials 1700, 1900,2100 with current conducting traces 1701, 1702, 1703, 1901, 2101 appliedto reduce electrical resistance within the metamaterials. The currentconducting traces 1701, 1702, 1703, 1901, 2101 provide an electricalpath for flowing electrons from the outer conductive layer 103 inmetamaterials 200, 300, 400 to collector contacts on the edges of thecells. Electrons may travel from the outer conductive layer 103 via thecurrent conducting traces 1701, 1702, 1703, 1901, 2101 to the outer edgeof the metamaterials 1700, 1900, 2100 where they connect to bus bars orhigh capacity conductors. By reducing the electrical resistance withinmetamaterials 1700, 1900, 2100 less electrical energy will be convertedto heat and more electrical power may be produced. The embodimentmetamaterials 1700, 1900, 2100 described below may include currentconducting traces 1701, 1702, 1703, 1901, 2101 in any combination orsub-combination.

FIG. 17 illustrates a cross-sectional side view of a metamaterial 1700,which is similar to metamaterial 200 but with current conducting traces1701, 1702, and 1703. In an embodiment, metamaterial 1700 may includecurrent conducting trace 1701 on top of the outer conductive layer 103of a row of shorter photovoltaic bristles 1704. Although FIG. 17 showsonly one row of shorter photovoltaic bristles 1704 with a currentconducting trace 1701 on the shorter photovoltaic bristles 1704, in anembodiment there may be multiple rows of shorter photovoltaic bristles1704 with current conducting traces 1701 on top.

In an embodiment, metamaterial 1700 may include current conductingtraces 1702, 1703 in different locations than current conducting trace1701. As with the current conducting trace 1701, metamaterial 1700 mayinclude current conducting trace 1702 on top of the outer conductivelayer 103, but positioned at the end of the array of photovoltaicbristles 201. Metamaterial 1700 may include current conducting trace1703 on top of the substrate 202 or in contact with the inner conductivelayer 107 to allow efficient electron flow. Electrons may flow from theabsorber sublayer 105 to the outer conductive layer 103 through thecurrent conducting traces 1701, 1702 to the electrical destination(e.g., electrical storage, electrical converter, or motor) and thecircuit is completed by connecting current conducting trace 1303 to theinner conductive layer 107 or metal substrate 202. Alternatively,electrons may flow from the absorber layer 105 through the innerconductive layer 107 to the current conducting trace 1303 and then to anelectrical destination (e.g., electrical storage, power converter, etc).

FIG. 18 illustrates the top view of FIG. 17 of metamaterial 1700 withcurrent conducting traces 1701, 1702, 1703. In an embodiment,metamaterial 1700 may include current conducting trace 1701 on top of anarray of shortened photovoltaic bristles 1704 extending along the widthof the array. Similarly, current conducting traces 1702 and 1703 mayextend along in the same direction of the array. Connecting currentconducting traces 1701 and 1702 to current conducting traces 1703 maycreate a complete circuit in the metamaterial 1700, thereby allowingcurrent to flow through the array of bristles when struck by photonssufficient to generate electron movement.

FIG. 19 illustrates a cross-sectional side view of a metamaterial 1900,which is similar to metamaterial 200, but with current conducting traces1901, 1702, 1703. In an embodiment, metamaterial 1900 may includecurrent conducting trace 1901 on the outer conductive layer 103 betweenthe photovoltaic bristles 201. As with FIG. 17, metamaterial 1900 mayinclude current conducting traces 1702 on the outer conductive layer 103and current conducting traces 1703 on the substrate 202 and/or incontact with the inner conductive layer 107. In contrast with FIG. 17,metamaterial 1900 may not include a row of shorter photovoltaic bristles1704 because current conducting traces 1901 are between the photovoltaicbristles 201 on top of the outer conductive layer 103. However, in anembodiment, metamaterial 1900 may include a row of shorter photovoltaicbristles 1704 with a current conducting trace 1701 on the shorterphotovoltaic bristles 1704 in addition to the current conducting traces1901 positioned between photovoltaic bristles 201.

FIG. 20 illustrates the top view of FIG. 19 of an array of photovoltaicbristles 201 on a flat substrate 202 with current conducting traces 1901positioned between photovoltaic bristles 201. Similar to the currentconducting traces 1701, 1702, 1703 in FIG. 18, the current conductingtraces 1901, 1702, and 1703 extend the entire width of the array. In anembodiment, the current conducting traces 1901, 1702, 1703 may extend inany direction. For example, the current conducting traces 1901, 1702,and 1703 may extend diagonally, along the length, and/or along the widthof the metamaterial 1900.

FIG. 21 illustrates a cross-sectional side view of a portion ofmetamaterial 2100 similar to metamaterial 300, but with currentconducting traces 2101, 1702, 1703. Metamaterial 2100 includes currentconducting trace 2101, which may be located between photovoltaicbristles 301 as well as at the peak and trough of the slanted substratesurfaces 308 a, 309 a, 308 b, 309 b. In an embodiment, metamaterial 2100includes current conducting traces 1702, 1703 at the ends of themetamaterial 2100 similar to FIGS. 17 and 19. Current conducting trace1702 may be on the outer conductive layer 103 at the ends of the arrayof photovoltaic bristles 301. Current conducting trace 1703 may be ontop of the substrate 302 and/or in contact with the inner conductivelayer 107. In an embodiment, metamaterial 2100 may include currentconducting traces 2101 on top of the outer conductive layer 103 andbetween photovoltaic bristles 301 located on the peak and/or the troughof the slanted substrate surfaces 308 a, 309 a, 308 b, 309 b. Althoughit is not shown in FIG. 21, the metamaterial 2100 may have currentconducting traces 2101 positioned on the outer conductive layer 103 ontop of shorter photovoltaic bristles 1704 as shown in FIG. 17. In anembodiment, metamaterial 2100 may be similar to metamaterial 400 as itmay be without photovoltaic bristles 401 on slanted substrate surfaces409 a, 409 b. For example, the metamaterial may include currentconducting traces 2101 between photovoltaic bristles 401 only onalternating slanted substrate surfaces 408 a, 408 b, etc.

Photolithographic techniques may be used to deposit the currentconducting traces 1701, 1702, 1703, 1901, and 2101 of FIGS. 17-21 onmetamaterials 200, 300, and 400. These current conducting traces may beadded to the metamaterials regardless of whether the metamaterials arecreated through stamping, vias, or any other technique. Althoughphotolithographic techniques are used for adding each current conductingtrace 1701, 1702, 1703, 1901, and 2101 to the metamaterial device, whenadding current conducting trace 1703 to a metamaterial a differentmethod may be used. Thus, FIGS. 22A-22F illustrate and FIG. 23 describesby the method steps for forming current conducting traces 1701, 1702,1901, and 2101, while FIGS. 24A-24J illustrate and FIG. 25 describes themethods steps for forming current conducting trace 1703. Each method isdiscussed in turn.

Current conducting traces 1701, 1702, 1901, and 2101 may be formed onmetamaterials 200, 300, and/or 400. In block 2302 a photoresist layermay be deposited over the metamaterial. As shown in FIGS. 22A and 22B, aphotoresist layer 189 may be deposited over the metamaterial. In block2304 a mask may be positioned over the photoresist layer. In block 2306the photoresist layer may be exposed to UV light through the mask. Asillustrated in FIG. 22C, exposing only a portion of the photoresist 189to UV radiation creates an exposed portion 189 a within the photoresistlayer 189. In block 2308 the photoresist layer 189 may be “developed” byexposing it to chemicals that remove the exposed portions 189 a leavinga protective template, and the assembly may be etched to create pores189 b shown in FIG. 22D. In optional block 2310 the substrate may beetched through the template. This step may be required when themetamaterial is formed with vias in methods 1400 or 1500. When creatingphotovoltaic bristles using vias, the original substrate 192 (shown inFIGS. 13K and 15I) may form a protective coating over the bristles.Thus, the method may include an etching step to expose the outerconductive layer 103 through the substrate 192 before depositing currentconducting traces 1701, 1702, 1901, and 2101 on the outer conductivelayer 103 eventually followed by filling the etched void in thesubstrate 192 with a transparent coating. In block 2322 a currentconducting trace may be deposited on the metamaterial. Currentconducting traces 1701, 1702, 1901, and 2101 may be deposited on theouter conductive layer 103 through a photoresist template as shown inFIG. 22E. In block 2312 the photoresist layer may be removed. As shownin FIG. 22F, when the photoresist 189 is removed, only the bristles andthe current conducting trace remains. After removing the photoresist, atransparent coasting may be applied to the solar cell covering thebristles and the deposited current conducting trace.

As an alternative to photolithographic techniques, a method fordepositing the current conductive traces may include an ink jet device2201 illustrated in FIGS. 22G and 22H to reduce manufacturing cost. Theink jet 2201 may deposit a conductive trace 1901 in desired locations(e.g., between bristles) by using colloidal material such as silverwithout the use of the multiple steps associated with photolithographictechniques. Thus, this alternative may include only one-step ofdepositing a conductive trace on the metamaterial in block 2322.

Current conducting trace 1703 may be formed by a different method asillustrated in FIGS. 24A-24J and FIG. 25. In block 2502 a firstphotoresist layer may be deposited over the metamaterial. As shown inFIG. 24A, a first photoresist layer 189 may be deposited over andbetween the bristles of the metamaterial. In block 2504 a first mask maybe positioned over the first photoresist layer. As shown in FIG. 24B,the first mask 195 may block UV radiation to the photoresist 189 exceptthrough mask portion 195 a. This controls the UV radiation to thedesired portion of the photoresist layer 189. In block 2506 the methodmay include exposing a UV source to the first photoresist layer throughthe first mask to create an etching template. As illustrated in FIG.24B, exposing only a portion of the photoresist layer 189 to UVradiation creates an exposed portion 189 a within the photoresist layer189. After creating the exposed portion 189 a within the photoresist,the mask may be subsequently removed from the metamaterial. In block2508 the first photoresist layer may be developed. For a positivephotoresist layer this includes removing the exposed portion 189 aleaving a template created by the remaining photoresist layer 189 withpores 189 b as shown in FIG. 24C. In block 2510 the method may includeetching the metamaterial through the etching template. As illustrated inFIG. 24D, the photoresist template 189 controls the etching process byremoving only a portion of the outer conductive layer 103, the firstabsorber layer 105, and the second absorber layer 104. In block 2512 thefirst photoresist layer may be removed. As shown in FIG. 24E, afterremoving the first photoresist layer 189, the metamaterial may include avoid in the outer conductive layer and the absorber layers. In block2514 a second photoresist layer may be deposited over the metamaterial.As shown in FIG. 24F the second photoresist layer 190 covers thebristles and the void in the metamaterial created by the etching step.In block 2516 a second mask may be positioned over the secondphotoresist layer. As shown in FIG. 24G, a second mask 196 may block theUV radiation to the second photoresist layer 190 except through thesecond mask portion 190 a. This controls the UV radiation to the desiredportion of the second photoresist layer 190. In block 2518 the methodmay include exposing a UV source to the second photoresist layer throughthe second mask. As illustrated in FIG. 24G, exposing only a portion ofthe second photoresist layer 190 to UV radiation creates a secondexposed portion 190 a within the second photoresist layer 190. Aftercreating the second exposed portion 190 a within the second photoresistlayer, the second mask may be subsequently removed from themetamaterial. In block 2520 the second photoresist layer may bedeveloped. For a positive photoresist this includes removing the secondexposed portion 190 a leaving a template created by the remaining secondphotoresist layer 190 with pores 190 b as shown in FIG. 24H. In block2522 a current conducting trace may be deposited on the metamaterial.The current conducting trace 1703 may be deposited on the innerconductive layer 107 through the second photoresist pore 190 b as shownin FIG. 24I. In block 2524 the second photoresist layer may be removed.As shown in FIG. 24J, when the second photoresist layer 190 is removed,only the bristles and the current conducting trace 1703 remains. Afterremoving the photoresist, a transparent coating may be applied to themetamaterial covering the bristles and the deposited current conductingtrace.

In another embodiment method that uses some of the same processes as inmethod 2500, the steps for etching may include laser ablation using awavelength-tuned laser to etch only the desired layers, as illustratedin FIGS. 24K through 24M. This may reduce the number of steps associatedwith the photolithographic techniques of method 2500 thereby reducingmanufacturing cost. As illustrated, a wavelength-tuned laser 2401 may beused to etch desired portions of the metamaterial for a conductivetrace. Since this technique provides a controlled etching alternative,it allows for any of the methods above to deposit current conductingtraces at any point within the method steps.

As an alternative embodiment to the conductive traces described above,high conductive regions may be applied to the various metamaterialsthough directional deposition such as solid angle physical vapordeposition or ion source deposition. The method may includepreferentially coating highly conductive regions with metal whileleaving other regions with minimal coating to refrain from blockingentering photons. For example, the method may include coating the areabetween the vias or bristles ten times as thick as the coating along thesidewalls of the vias or bristles allowing photons to pass through thesidewalls while simultaneously creating a highly conductive region toact as a conductive trace. As another example, the method may includeusing a thicker conductive coating only on the side of bristles or viasthat will receive less exposure to photons during operation of thecompleted metamaterial. To accomplish the single region deposition, themethod may include angling the substrate during the deposition processso that only the desired side receives the highly conductive coating.Regardless of the exact process, the conductive regions may be appliedto any of the methods listed above.

Metamaterials 200, 300, 400, 1700, 1900, and 2100 formed by any of theprocesses above may be assembled into a solar panel. As brieflydescribed above, the corrugated shape may be incorporated into anassembled solar panel as illustrated in FIGS. 26-32. The panel assemblymay include a corrugated base with panel surfaces angled atapproximately 30 to 60 degrees for increasing off-axis photon absorptionin metamaterials 200 with flat substrates as well as increasing theplanar bristle density without increasing shadowing, resulting insimilar gains in total efficiency and power generation frommetamaterials 300, 400 with corrugated substrates. However, the totalefficiencies gains are compounded when the panel assembly andmetamaterials include a corrugated shape (e.g., metamaterial 300 in acorrugated solar panel assembly) because the assembled panel benefitsfrom an increase in planar bristle density and off-axis photonabsorption.

FIGS. 26-32 illustrate an embodiment solar panel 3100 with a corrugatedbase 2610. Solar panels with a corrugated base 2610 may be formed byassembling metamaterials 200, 300, 400, 1700, 1900, and/or 2100together. FIG. 26 illustrates a perspective view of a section of a solarpanel 2600. Solar panel section 2600 may include one or more panelsurfaces 2602, 2604 in an alternating fashion on a corrugated base 2610.In an embodiment, each panel surface 2602, 2604 may includemetamaterials 200, 300, 400, 1700, 1900, and/or 2100 with photovoltaicbristles 201, 301, 401. In an embodiment, panel surfaces 2602, 2604 mayinclude the same metamaterial. For example, each panel surface 2602,2604 may include metamaterials 200 with a flat substrate 202. In anembodiment, panel surfaces 2602, 2604 may include differentmetamaterials. For example, panel surfaces 2602 may includemetamaterials 200 with flat substrates 202 while panel surfaces 2604 mayinclude metamaterials 300 with corrugated substrates 302. In anembodiment, a first panel surface 2602 may include metamaterials 200,300, 400, 1700, 1900, and/or 2100, while a second panel surface 2604 iswithout metamaterial 200, 300, 400, 1700, 1900, and/or 2100. Forexample, solar panel section 2600 may include a first panel surface 2602with metamaterials 300 alternating along a corrugated base 2610 with asecond panel surface 2604 without metamaterials. In an embodiment, asecond panel surface 2604 without metamaterials 200, 300, and/or 400 mayinclude a reflective film (i.e., a mirror). For example, the first andsecond panel surfaces 2602, 2604 may alternate along the corrugated base2610 with a first panel surface 2602 with metamaterials 400 and a secondpanel surface 2604 with only a reflective film. Regardless, each panelsurface 2602, 2604 rests on the front of a corrugated base 2610.

In an embodiment, fasteners 2612 may be used to fasten the panelsurfaces 2602, 2604 to the corrugated base 2610 with connectors 2608.The same fastener 2612 may also fasten the rails 2902 (shown in FIG. 29)to the corrugated base 2610 and the connectors 2608. In an embodiment,solar panel section 2600 may include a buss bar 2606 with connectors2608 to connect the buss bar 2606 to each metamaterial 200, 300, 400,1700, 1900, and/or 2100 of the panel surfaces 2602, 2604. In anembodiment, the buss bar 2606 may connect to the corrugated base 2610 ina slot 2614 of the corrugated based 2610. The slot 2614 may providestability for the buss bar 2606 as well as allow solar panel section2600 to rest on a flat back of the corrugated base 2610.

FIG. 27 illustrates a top view of solar panel section 2600. Asillustrated with FIG. 26, the solar panel section 2600 may include panelsurfaces 2602, 2604, a corrugated base 2610, a buss bar 2606, fasteners2612, and connectors 2608.

FIG. 28 illustrates a side view of solar panel section 2600. Asillustrated, the connectors 2608 may use a single fastener 2612 for eachpair of panel surfaces 2602, 2604. The fastener 2612 may be any means offastening the connectors 2608 to the corrugated base 2610 and the panelsurfaces 2602, 2604. For example, the fasteners 2612 may utilize a bolt,a joint, a rivet, screws, a pin, clips, latch, etc. In an embodiment,the fastener 2612 may be metal or metalized to create an electricalpathway from the metamaterials 200, 300, 400, 1700, 1900, and/or 2100 ofpanel surfaces 2602, 2604 to the connectors 2608. As referenced in FIG.26, the corrugated base 2610 may have a slot 2614 for the buss bar 2606.The slot 2614 may allow the buss bar 2606 to connect to the backside ofthe corrugated base 2610 and form a flat surface (i.e. flat back) of thecorrugated base 2610. The flat surface of the backside of the corrugatedbase 2610 may allow for a more stable assembly for the completed solarpanel 2600.

FIG. 29 illustrates an exploded view of a solar panel section 2600. Asillustrated, rail 2902 may be secured to the corrugated base 2610 by asecuring mechanism 2901. The rail 2902 may be secured to the corrugatedbase 2610 by any means possible. For example, the rail 2902 may besecured to the backside of the corrugated base 2610 by a rivet,crimping, a bolt, adhesive or any other securing means. In anotherexample, the rail 2902 may be secured to the corrugated base 2610similar to a fastener 2612 used to fasten the panel surfaces 2602, 2604to the corrugated base 2610. In an embodiment, the rail 2902 also may befastened by the fastener 2612 to panel surfaces 2602, 2604 on thebackside of the corrugated base 2610 opposite the connectors 2608. In anembodiment, the rail 2902 may be fastened to the panel surfaces 2602,2604 by any means possible including the fastening means as describedwith reference to FIG. 28. In an embodiment, the buss bar 2606 may besecured to the corrugated base 2610 by a securing mechanism 2901. In anembodiment, the buss bar 2606 may be attached to the rail 2902 with anattachment mechanism 2904. The attachment mechanism 2904 may be anymeans of attachment. The attachment mechanism may be the same as thesecuring mechanisms 2901, or the fasteners 2612 as described above.

In an embodiment, the rails 2902 and the buss bars 2606 may beelectrically connected to the metamaterials 200, 300, 400, 1700, 1900,and/or 2100 of panel surfaces 2602, 2604. In an embodiment, the rails2902 may be electrically connected to connectors 2608. The connectors2608 may be electrically connected to the panel surfaces 2602, 2604including metamaterials 200, 300, 400, 1700, 1900, and/or 2100. Themetamaterials 200, 300, 400, 1700, 1900, and/or 2100 may create electronmovement when the photovoltaic bristles 201, 301, 401 are struck byphotons. In an embodiment, the outer conductive layer 103 ofmetamaterials 200, 300, 400 illustrated in FIGS. 2B, 3B, and 4B may beelectrically connected to connectors 2608. In an embodiment the currentconducting traces 1701, 1702, 1703, 1901, and/or 2101 of metamaterials1700, 1900, 2100 as illustrated in FIGS. 17, 19, and 21 may beelectrically connected the connectors 2608 to help reduce the electricalresistance in the metamaterial 1700, 1900, 2100. Regardless, electronmovement may create electricity to flow from the metamaterials 200, 300,400, 1700, 1900, and/or 2100 within the panel surfaces 2602, 2604 to theconnectors 2608 to the rails 2902 and buss bars 2606 connected to therails 2902. From the rails 2902 and buss bars 2606, the electricity mayflow to other rails 2902 and buss bars 2606 in neighboring panelsections 2600 and eventually to an electrical destination (e.g.electrical storage) connected to the completed solar panel 3100.

FIG. 30 illustrates a back view of a solar panel section 2600. Asdiscussed earlier, the buss bar 2606 of the solar panel section 2600 mayhave a securing mechanism 2901 to help stabilize the buss bar 2606 onthe backside of the corrugated section 2600. In an embodiment, each bussbar 2606 may have one or more securing mechanism 2901 to secure the bussbar 2606 to the back of the corrugated base 2610. Alternatively, eachbuss bar 2606 may not have a securing mechanism 2901 with the corrugatedbase 2610 and may be secured and connected only with the rails 2902.Although FIGS. 26-30 depict a solar panel section 2600 with two rails2902 and two buss bars 2606, a solar panel section 2600 may have anynumber of rails 2902 and buss bars 2606. Some examples of solar panelsections 2600 with a different number of rails include solar panelsections with one rail, two rails, three rails, four rails, five rails,etc. Some other examples of solar panel sections with a different numberof buss bars include panel sections with one buss bar, two buss bars,three buss bars, four buss bars, five buss bars, etc.

FIG. 31 illustrates a perspective view of a solar panel 3100 withmultiple solar panel sections 2600. In an embodiment, each solar panelsection 2600 may include metamaterials 200, 300, 400. In anotherembodiment, the metamaterials may include current conducting traces1701, 1702, 1703, 1901, 2101 as illustrated in metamaterials 1700, 1900,or 2100 of FIGS. 17, 19, and 21. In an embodiment, each solar panelsection 2600 may be adjacent and combine with one or more other solarpanel sections 2600. In an embodiment, the solar panel 3100 may includea frame 3102 that surrounds the outer perimeter of the combined solarpanel sections 2600 within the solar panel 3100.

FIG. 32 illustrates an exploded view of a solar panel 3100. In anembodiment, the solar panel 3100 may include a frame 3102, a top cover3202, and a back cover 3208. In an embodiment, the frame 3102 isconnected with corner brackets 3206 and fasteners 3204 to the corners ofsolar panel sections 2600 positioned in the corners of solar panel 3100.In an embodiment, the frame 3102 for solar panel 3100 may include twoshort pieces 3214 a, 3214 b and two long pieces 3216 a, 3216 b to attachalong the four sides of the assembled solar panel sections 2600. In anembodiment, the solar panel 3100 may have four or more corner brackets3206 (e.g., eight as shown) to connect the pieces of the frame 3102 tothe assembled solar panel sections 2600.

In an embodiment, the top cover 3202 of the solar panel 3100 may betransparent or semitransparent. The top cover 3202 may protect the solarpanel section 3100 and their electrical and photovoltaic components. Forexample, the top cover 3202 may protect the solar panel section 2600 andtheir electrical and photovoltaic components from oxygen corrosion,wind, water, and dirt or anything else that may reduce the efficiency orlife of the metamaterials 200, 300, 400, 1700, 1900, and/or 2100 insolar panel 3100.

In an embodiment, the back cover 3208 of solar panel 3100 may includerounded slots 3212 so that fasteners 3210 may connect the back cover3208 to the assembled (i.e., combined) solar panel sections 2600. Thefasteners 3210 may be any type that may connect the back cover 3208 tothe assembled solar panel sections 2600. For example, the fasteners 3210may fasten similar to the fasteners 2612 as described with reference toFIG. 28 (e.g., by bolts, screws, etc.).

In an embodiment, the back cover 3208 and the top cover 3202 may besealed within the solar panel 3100 by the frame 3102. In an embodiment,only the back cover 3208 or the top cover 3202 may be sealed within thesolar panel 3100 by the frame 3102. The back cover 3208 and the topcover 3202 may provide structural support to the solar panel 3100 andits subparts. In addition, the back cover 3208 and the top cover 3202may protect the subparts of the solar panel 3100 from any contaminationthat may reduce the efficiency and life of the metamaterials 200, 300,400, 1700, 1900, and/or 2100 in solar panel 3100 such as wind, water,dirt, or oxygen, etc.

In another embodiment, the volumetric efficiency gains realized from thesolar panel with the corrugated sections may be achieved by mountingcompleted solar panels in corrugated patterns with respect to eachother. Thus, completed solar panels may be mounted in an array of solarpanels where the surfaces of each solar panel form an angle ofapproximately 30 to 60 degrees with a common plane such as a baseconnecting the solar panels that is perpendicular to the sun. As analternative embodiment, reflectors may replace some completed solarpanels in the corrugated pattern to help maximize efficiency gain ofeach completed solar panel.

Referring to FIG. 37A, a first exemplary in-process photovoltaicstructure is illustrated. As used herein, an “in-process” structure or a“prototypical” structure refers to a transient structure that issubsequently modified by addition of another material, removal of anexisting material, or a combination thereof to provide a final devicestructure.

The first exemplary in-process photovoltaic structure may include afinal substrate 3609 d as provided by the processing steps of FIG. 36A.The final substrate 3609 d may include a sheet substrate 3710 and amoldable material layer 3720 that is an optically transparent layer,i.e., a layer composed of an optically transparent material. As usedherein, an “optically transparent material” refers to a material havingan absorption coefficient that is less than 100 cm⁻¹ between the entirewavelength range from 400 nm to 800 nm. In an embodiment, the opticallytransparent material of the moldable material layer 3720 may have anabsorption coefficient that is less than 10 cm⁻¹ between the entirewavelength range from 400 nm to 800 nm. In another embodiment, theoptically transparent material of the moldable material layer 3720 mayhave an absorption coefficient that is less than 1 cm⁻¹ between theentire wavelength range from 400 nm to 800 nm.

The refractive index of the moldable material layer 3720 may be in arange between 1 and 3 between the wavelength range from 400 nm to 800nm. In an embodiment, the refractive index of the moldable materiallayer 3720 may be in a range between 1.2 and 2.4 between the wavelengthrange from 400 nm to 800 nm. In another embodiment, the refractive indexof the moldable material layer 3720 may be in a range between 1.3 and2.0 between the wavelength range from 400 nm to 800 nm. In anembodiment, the refractive index of the moldable material layer 3720 maybe in a range between 1.4 and 1.7 between the wavelength range from 400nm to 800 nm.

The moldable material layer 3720 may be a dielectric material layer. Theresistivity of the moldable material layer 3720 may be greater than1.0×10⁵ Ohm-cm. In an embodiment, the resistivity of the moldablematerial layer 3720 may be greater than 1.0×10⁶ Ohm-cm. In anotherembodiment, the resistivity of the moldable material layer 3720 may begreater than 1.0×10⁷ Ohm-cm.

In an embodiment, the sheet substrate 3710 may be an opticallytransparent substrate, and may, or may not, be flexible. In anembodiment, the sheet substrate 3710 may include a rigid material suchas glass (including doped or undoped silicate glass) or sapphire. Inanother embodiment, the sheet substrate 3710 may include a transparentflexible material such as transparent polymers (e.g., plastics). Thesheet substrate 3710 may be a continuous sheet extending for hundreds offeet and stored in a roll, or may be discrete sheet having lateraldimensions on the order of 1 m and stored, for example, by stacking.

A metamaterial of the present disclosure may be formed by providing amoldable material layer 3720 on, or in, a sheet substrate 3710. In anembodiment, the moldable material layer 3720 may be formed on the sheetsubstrate 3710 by dispensing a moldable material on the sheet substrate3710. The moldable material may be any optically transparent materialthat may be molded. The thickness of the moldable material layer 3720,prior to patterning by imprinting or alternative means, may be in arange from 6 microns to 1 mm, and typically in a range from 10 micronsto 60 microns, although lesser and greater thicknesses may also beemployed.

In an embodiment, the moldable material layer 3720 may contain amoldable material selected from a lacquer, a silicone precursormaterial, a gel derived from a sol containing a polymerizable colloid,and a glass transition material. In an embodiment, the moldable materiallayer 3720 may include a polymer resin-based plastic material, anorganic material including at least one resin, or a flexible glassmaterial based on silica. The transparent sheet substrate 3710 mayinclude a plastic film or a glass film that is more rigid than themoldable material layer 3720. In one embodiment, the moldable materiallayer 3720 may be provided by applying a polymerizable material on asubstrate (such as the sheet substrate 3710), and inducing partialpolymerization of the polymerizable material.

In embodiments in which the moldable material layer 3720 includes alacquer, the moldable material may be selected from phenylalkylcatechol-based lacquers, nitrocellulose lacquers, acrylic lacquers, andwater-based lacquers. Phenylalkyl catechol-based lacquers include atleast one phenylalkyl catechol that includes a long alkyl chain.Examples of such phenylalkyl catechols include urushiol and laccol (alsoreferred to as thitsiol). Urushiol has the formula of C₆H₃(OH)₂R, inwhich R may be, for example, (CH₂)₁₄CH₃ or (CH₂)₇CH═CHCH₂CH═CHCH₂CH═CH,or a similar radical. Laccol is a crystalline phenol having the formulaof or (CH₂)₇CH═CHCH₂CH═CH(CH₂)₂CH₃ or (CH₂)₇CH═CH(CH₂)₅CH₃ or(CH₂)₇CH═CHCH₂CH═CHCH═CHCH₃. Laccol has the formula of C₁₇H₃₁C₆H₃(OH)₂(i.e., C₆H₃(OH)₂R in which R=C₁₇H₃₁) and occurring in the sap of lacquertrees. Phenylalkyl catechol-based lacquers are generally slow-drying,and are set by oxidation and polymerization in addition to evaporationalone. Heat and humidity may be applied to accelerate partial setting ofthe phenylalkyl catechol-based lacquers prior to imprinting and/or toaccelerate full setting of the phenylalkyl catechol-based lacquers afterimprinting. The phenols oxidize and polymerize under the action of anenzyme laccase, yielding a substrate that, upon proper evaporation ofits water content, is hard.

Nitrocellulose lacquers are fast-drying solvent-based lacquers thatcontain nitrocellulose, which is a resin obtained from the nitration ofa cellulostic material (such as cotton). Nitrocellulose lacquers may beapplied by spraying. Nitrocellulose lacquers produce a flexible, hard,and transparent film.

Acrylic lacquers refer to lacquers using acrylic resin (which is asynthetic polymer). Acrylic resin is a transparent thermoplastic that isobtained by the polymerization of derivatives of acrylic acid. Acryliclacquer has a fast drying time.

Water-based lacquers are less toxic than other types of lacquers, andvarious types of water-based lacquers are known. An illustrativeexemplary composition for water-base lacquer may be acrylic CopolymerResin 30% in weight percentage, dipropylene glycol monomethyl ether atabout 5% in weight percentage, propylene glycol monomethyl ether atabout 5% in weight percentage, and water in about 60% weight percentage.Other exemplary compositions for water-based lacquer are disclosed, forexample, in European Patent Publication No. EP0555830 A1 and U.S. Pat.No. 5,550,179 A.

In an embodiment, the moldable material layer 3720 may include a plasticmaterial prepared from semicrystalline or amorphous polymer resins.Examples of semicrystalline resins that may be employed for the moldablematerial layer 3720 include, but are not limited to, terephthalate(PET), polypropylene (PP), high density polyethylene (HDPE), low densitypolyethylene (LDPE), nylon, polyoxymethylene (POM), polybutyleneterephthalate (PBT), polytetrafluoroethylene (PTFE), polyvinylidenefluoride (PVFD), polyethylenechlorotrifluoroethylene (PECTFE),polyethylene tetrafluoroethylene (PETFE), or similar fluoro-based andnon-fluoro-based polymers blended together or copolymerized in one ormore mixtures. In an embodiment, the moldable material layer 3720 mayinclude terephthalate (PET). Examples of amorphous polymer resinsinclude, but are not limited to, polycarbonate (PC),polymethylmethacrylate (PMMA), polymethacrylate (PMA), cyclic polyolefin(branded under the trade name Topas™), or similar polymers blendedtogether or copolymerized in one or more mixtures.

In an embodiment, the moldable material layer 3720 may include a resinmaterial. In an embodiment, the resin material may be selected such thatthe resin material may be cured with a radiation with wavelengthsbetween 200 nm and 450 nm (such as 365 nm), or may be cured or setthermally with heat treatment at a temperature in a range from 500° C.to 500° C.

In an embodiment, the resin material of the moldable material layer 3720may be selected from radiation cured organic materials that are curedthrough radical polymerization of methacrylate and methylmethacrylatemonomers, preferably methylmethacrylate monomers and methylmethacrylatederivations. Example of methylmethacrylate derivations include by notlimited to methylmethylacrylic acid, hydroxyethylmethylmethacrylate,fluorofunctinoalized methylmethacrylate, and silicone-functionalizedmethylmethacrylate. These may be mixed in various proportions andblended with oligomers based on urethane acrylate precursors andphotoinitiators activated by light in the wavelength range listed above.

In another embodiment, the resin material of the moldable material layer3720 may be selected from radiation cured organic materials curedthrough cationic polymerization using a cationic photoinitiatorsactivated by light in the wavelength range above. Monomers are epoxybased with single, double, or multiple functionality. Monomer examplesinclude, but are not limited to, diglycidyl monomers based onbisphenol-A or bisphenol-F, cylic aliphatic monomers and oligomers, andmixtures thereof.

In another embodiment, the resin material of the moldable material layer3720 may be selected from thermally cured sol-gel based chemistries thatundergo hydrolysis and condensation reactions resulting in highlycrosslinked inorganic matrices. Examples include but not limited totetraethylorthosilicate (TEOS), tetramethylorthosilicate (TMOS), ororganically modified silicates with one or more hydrolyzeablecomponents, or mixtures thereof. These resin materials may be furthersintered at an elevated temperature between 300° C. and 500° C. todensify the silicate, evaporate low molecular weight byproducts, andpyrolyze the organic materials to form a high temperature resistantceramic.

In another embodiment, the resin material of the moldable material layer3720 may be selected from thermally cured silicates that are crosslinkedthrough hydrosilation addition reactions using platinum catalysts whichmay be sintered at an elevated temperature between 300° C. and 500° C.to densify silicate and pyrolyze away the organic materials to form atemperature resistant ceramic.

In another embodiment, the resin material of the moldable material layer3720 may be selected from organic-inorganic hybrid resins based onradiation cured silicates from monomers of acrylate and methacrylatefunctionality that may be cured with radical polymerization afteractivation of photoinitiators irradiated with light in the wavelengthrange above and undergo further densification by sol-gel condensation ofhydroxysiloxane groups in the materials. These materials may then besubsequently sintered at an elevated temperature between 300° C. and500° C. to form a high temperature resistant ceramic.

In another embodiment, the resin material of the moldable material layer3720 may be selected from a solid deformable material, which may be athermoset or thermoplastic resin, that may be applied through a solventcast method and may be laminated as a film. Examples of thermoset resinsinclude, but are not limited to, epoxies, polyurethanes, silicones,ethylene propylene diene monomer (EPDM) rubber, and nitrile and naturalrubbers. Examples of thermoplastic resins include both semi-crytallineand amorphous resins. Semi-crystalline polymer resins include, but arenot limited to, polyethylene terephthalate (PET), polypropylene (PP),high density polyethylene (HDPE), low density polyethylene (LDPE),nylon, polyoxymethylene (POM), polybutylene terephthalate (PBT),polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVFD),polyethylenechlorotrifluoroethylene (PECTFE), polyethylenetetrafluoroethylene (PETFE), and similar fluoro-based andnon-fluoro-based polymers blended together or copolymerized in one ormore mixtures. For films embossed with an imprinting lacquer, PET may beemployed. For films embossed with heat and pressure, PE may be employed.Amorphous polymer resins include, but are not limited to, polycarbonate(PC), polymethylmethacrylate (PMMA), polymethacrylate (PMA), cyclicpolyolefin (branded under the trade name Topas™), and similar polymersblended together or copolymerized in one or more mixtures.

In an embodiment, the moldable material layer 3720 may include amoldable material that may form silicone, i.e., a silicone precursor.Silicones are polymers that include any inert, synthetic compound madeup of repeating units of siloxane, which is a functional group of twosilicon atoms and one oxygen atom, and may be combined with carbonand/or hydrogen. In an embodiment, the moldable material of the moldablematerial layer 3720, as applied to the sheet substrate 3710 prior toimprinting, may be selected from polydimethylsiloxane,dimethyldichlorosilane, methyltrichlorosilane, andmethyltrimethoxysilane.

In an embodiment, the moldable material layer 3720 may be formed byapplying a precursor material for polydimethylsiloxane (PDMS;CH₃[Si(CH₃)₂O]_(n)Si(CH₃)₃) and inducing the polymerization of theprecursor material. The number n of repetition of the monomer[SiO(CH₃)₂] units determines the viscosity and elasticity of thepolydimethylsiloxane material. The polymerization reaction evolveshydrogen chloride.

Silane precursors with more acid-forming groups and fewer methyl groups,such as methyltrichlorosilane, may be used to introduce branches orcross-links in the polymer chain, thereby producing hard siliconeresins. Alternatively, chlorine atoms in the silane precursor forpolydimethylsiloxane may be replaced with acetate groups. In this case,the polymerization produces acetic acid, which is less chemicallyaggressive than HCl. After polymerization and cross-linking, a siliconeprecursor material produces an optically transparent layer having ahydrophobic surface.

In an embodiment, the moldable material layer 3720 may contain a sol-gelmaterial. As used herein, a sol-gel material refers to a sol materialthat may be subsequently transformed to a gel material or a gel materialthat is derived from a sol material, i.e., a material that may gothrough a sol-gel transition or has gone through a sol-gel transition.The moldable material layer 3720 as applied to the sheet substrate 3710may be a sol material, which subsequently goes through a sol-geltransition to become a gel material prior to imprinting.

A sol-gel transition or a sol-gel process refers to a process in which asol (a set of solid nanoparticles and a liquid in a state in which thesolid particles are dispersed in the liquid) agglomerate to form a gel(a set of a liquid and a continuous three-dimensional network extendingthroughout the liquid). A sol is a colloid. A colloid is a mixture inwhich at least two different phases (such as solid and liquid) areintimately mixed at microscopic level. Solid nanoparticles ormacromolecules are dispersed throughout the liquid in a sol. In a gel,the solid network of interconnected nanostructures spans the volume of aliquid medium. In the gel, the continuous phase is a solid network andthe dispersed phase is a liquid. A sol may become a gel when the solidnanoparticles dispersed in it may join together to form a network ofparticles that spans the liquid. As a sol becomes a gel, its viscosityapproaches infinity and finally becomes immobile. A sol-gel transitionmay be triggered with the passage of time, change of pH, addition of agelation agent, temperature, agitation, and/or catalysts.

In an embodiment, the moldable material of the moldable material layer3720 as applied to the sheet substrate 3710 may be a sol-gel materialselected from a colloid containing a metal alkoxide and a colloidcontaining silicon alkoxide. In this case, hydrosis and condensation maybe employed to form a gel from the sol so that the moldable materiallayer 3720 as provided for imprinting is in a gel state.

The precursor sol may be either deposited on a substrate to form a film(e.g., by dip coating or spin coating), cast into a suitable containerwith the desired shape (e.g., to obtain monolithic ceramics, glasses,fibers, membranes, aerogels), or used to synthesize powders (e.g.,microspheres, nanospheres).

A typical sol-gel process includes solution, gelation, optional drying,and optional densification operations. In one exemplary embodiment, themoldable material layer 3720 may include an incompletely dried orincompletely densified silica glass. An alkoxide may be mixed with waterand a mutual solvent to form a solution. During gelation, hydrolysisleads to the formation of silanol groups (Si—OH), which are intermediategroups. The moldable material layer 3720 as provided for imprinting mayinclude silanol groups. Optionally, a partial condensation reaction thatproduces siloxane bonds (Si—O—Si) may be performed prior to imprinting.A second condensation reaction may be performed after imprinting.Alternatively, the condensation reaction may be performed only afterimprinting. The silica gel formed by this process leads to aninterconnected three-dimensional network including polymeric chains.Thus, drying and densification may be performed after imprinting of themoldable material layer 3720.

If a sol-gel material selected from a colloid containing a metalalkoxide and a colloid containing silicon alkoxide may be applied as themoldable material layer 3720 on the sheet substrate 3710, hydrosis andcondensation may be employed to form a gel from the sol so that themoldable material layer 3720 as provided for imprinting is in a gelstate. In an embodiment, a silicon alkoxide such as silicontetraethoxide (Si(OC₂H₅)₄, i.e., tetraethyl orthosilicate (TEOS)) may beemployed as the sole material for the moldable material layer 3720. In asubsequent hydrolysis (reaction with water), a hydroxyl ion becomesattached to the silicon atom as follows:Si(OC₂H₅)₄+H2O→HO—Si(OC₂H₅)₃+C₂H₅—OH

In an embodiment, the amount of water added to silicon tetraethoxide forhydrolysis may be controlled such that hydrolysis proceeds partially,and does not result in 100% conversion of silicon tetraethoxide intosilica, but provides a gel including polymer chains of intermediatespecies a partial hydrolysis reaction such as HO—Si(OC₂H₅)₃ and/or(HO)₂—Si(OC₂H₅)₂. The moldable material layer 3720 as provided forimprinting includes such a gel. After imprinting, complete hydrolysismay be performed by providing additional water and optionally employinga hydrolysis catalyst such as acetic acid or hydrochloric acid.

Formation of a metal oxide involves connecting the metal centers withoxo (M-O-M) or hydroxo (M-OH-M) bridges, therefore generating metal-oxoor metal-hydroxo polymers in solution.

In an embodiment, the moldable material layer 3720 may include aflexible glass material based on silica (SiO₂) manufactured andprocessed with a roll-to-roll manufacturing method. In an embodiment,the moldable material layer 3720 may include glass film commerciallyavailable from the glass manufacturer Corning™ and branded as WillowGlass™.

The web-to-plate system may include a first densification deviceconfigured to reduce elasticity of the moldable material priorimprinting, and/or a second densification device configured to reduceelasticity of the moldable material after imprinting. In an embodiment,each of the first and second densification devices may include at leastone of a fan, a heater, an ultraviolet treatment system, an agitator,and a laser irradiation system. The first and/or second densificationdevice may optionally include a spray device configured to spray agelation accelerant or a catalyst that accelerates densification of themoldable material at various stages of densification.

In an embodiment, the pattern in the moldable material layer 3720 may bemade by embossing the moldable material layer 3720 with a patternedmetal plate with heat and pressure in case the moldable material layer3720 includes a plastic or glass film, or may be made by embossing animprinting resin on the plastic or glass film and subsequently curingthe imprinting resin while in contact with the patterned metal plate incase the moldable material layer 3720 includes the resin.

During the imprinting process, a die (such as a daughter die web 3501 din FIG. 36A) including a pattern of protruding structures andincorporated into a web may be imprinted onto the moldable materiallayer 3720 to generate a pattern of trenches 1103 extending downwardfrom a top surface of the moldable material layer 3720 to a depth, whichmay be the same as the height h of the trench 1103. The height h of thetrenches 1103 may be the same as the height h of the bristles discussedabove. In an embodiment, the height h of the trench 1103 may be lessthan the thickness t of the moldable material layer 3720. In anembodiment, the thickness t of the moldable material layer 3720 may bein a range from 6 microns to 200 microns. In another embodiment, thethickness t of the moldable material layer 3720 may be in a range from10 microns to 100 microns. In yet another embodiment, the thickness t ofthe moldable material layer 3720 may be in a range from 15 microns to 30microns.

In an embodiment, each of the trenches 1103 may have a height h in arange from 3 microns to 100 microns, although lesser and greater depthsmay also be employed. In an embodiment, each of the trenches 1103 mayhave a height h in a range from 6 microns to 30 microns. In anotherembodiment, each of the trenches 1103 may have a height h in a rangefrom 9 microns to 15 microns. In another embodiment, each of thetrenches 1103 may have a height h in a range from 10 microns to 12microns. In another embodiment, the trenches 1103 may have the samedepth.

A base lateral dimension bd may be in a range from 0.4 micron to 20microns at the top portion of each trench 1103, although lesser andgreater dimensions may also be employed. As used herein, a base lateraldimension bd refers to the maximum lateral dimension at the topmostportion of a trench 1103. The base lateral dimension becomes the basedimension of an inverted trench after the first exemplary structure issubsequently flipped upside down. The horizontal cross-sectional shapeof each trench 1103 may be in a circular shape, an elliptical shape, ora closed curvilinear shape. In an embodiment, the horizontalcross-sectional shape of each trench 1103 may be a circle, and the baselateral dimension bd may be the diameter of each trench 1103 at atopmost portion, i.e., the portion that is most distal from theinterface between the moldable material layer 3720 and the transparentsheet substrate 3710. In an embodiment, the base lateral dimension bdmay be in a range from 1 micron to 10 microns. In another embodiment,the base lateral dimension bd may be in a range from 2 microns to 9microns. In yet another embodiment, the base lateral dimension bd may bein a range from 4 microns to 8 microns. In another embodiment, the baselateral dimension bd may be in a range from 5 microns to 7 microns.

A tapered-end lateral dimension td may be in a range from 0.22 micron to12 microns at the top portion of each trench 1103, although lesser andgreater dimensions may also be employed. As used herein, a tapered-endlateral dimension td refers to the maximum lateral dimension at thebottommost portion of a trench 1103. The tapered-end lateral dimensionbecomes the dimension of the tapered upper portion of an inverted trenchafter the first exemplary structure is subsequently flipped upside down.In an embodiment, the horizontal cross-sectional shape of each trench1103 may be a circle, and the tapered-end lateral dimension td may bethe diameter of each trench 1103 at a bottommost portion, i.e., theportion that is most proximal to the interface between the moldablematerial layer 3720 and the transparent sheet substrate 3710. In anembodiment, the tapered-end lateral dimension td may be in a range from0.6 micron to 6 microns. In another embodiment, the tapered-end lateraldimension td may be in a range from 1.2 microns to 4.8 microns. Inanother embodiment, the base lateral dimension bd may be in a range from2.4 microns to 3.6 microns. In another embodiment, the base lateraldimension bd may be in a range from 3 microns to 4.2 microns.

The ratio of the base lateral dimension bd to the height h of the trench1103 may be in a range from 0.5 to 0.75, although lesser and greaterratios may also be employed. In an embodiment, the ratio of the baselateral dimension bd to the height h of the trench 1103 may be in arange from 0.55 to 0.7. In another embodiment, the ratio of the baselateral dimension bd to the height h of the trench 1103 may be in arange from 0.6 to 0.65.

The horizontal cross-sectional shape of each trench 1103 may becircular, elliptical, polygonal, or of any other closed curvilinearshape. In an embodiment, the horizontal cross-sectional shape of eachtrench 1103 may be substantially circular. The sidewall of each trench1103 may be substantially vertical, or may be tapered with a taper angleα in a range from 3 degrees to 15 degrees, although greater taper anglesmay also be employed. As used herein, a surface is substantiallyvertical if the angle of the surface with respect to a verticaldirection does not exceed 3 degrees. In an embodiment, the taper angle αmay be in a range from 6 degrees to 10 degrees. In another embodiment,the taper angle α may be in a range from 7 degrees to 9 degrees.

After imprinting, the material of the moldable material layer 3720 withan imprint pattern thereupon may be densified or otherwise transformedto increase the rigidity. For example, if the moldable material layer3720 includes a lacquer, a silicone, or a gel, densification oradditional transformation of the moldable material layer 3720 may beeffected by heat, cold, moisture, agitation, application of a catalyst,irradiation by visible light, ultraviolet light, or infrared light,ventilation, or a combination thereof. In one embodiment, if themoldable material layer 3720 is provided by applying a polymerizablematerial on a substrate (such as the sheet substrate 3710) andsubsequently inducing partial polymerization of the polymerizablematerial, the patterned moldable material layer 3720 may be cured forfurther polymerization after patterning and prior to depositing a layerstack, or after depositing the layer stack.

In case the moldable material layer 3720 after imprinting includes agel, further polycondensation process may be performed to enhancemechanical properties and structural stability by application of heat toinduce sintering, densification and/or grain growth. Optionally, adrying process may be employed to remove any residual liquid (solvent)in the moldable material layer 3720.

The moldable material layer 3720 after densification or rigidificationfunctions an optically transparent template on which material layers forforming a photovoltaic structure may be sequentially deposited.

Referring to FIG. 37B, an outer conductive layer 103 may be deposited onthe contiguous top surface of the moldable material layer 3720, whichincludes a planar top surface and surfaces of the trenches 1103. Theouter conductive layer 103 may be the same as described above. In anembodiment, the outer conductive layer 103 may be a transparentconductive material layer, and may contain, for example, a transparentconductive oxide such as indium tin oxide (ITO), fluorine doped tinoxide (FTO), and doped zinc oxide.

The outer conductive layer 103 may be deposited, for example, bysputtering (physical vapor deposition), metal organic chemical vapordeposition (MOCVD), metal organic molecular beam deposition (MOMBD),spray pyrolysis, or pulsed laser deposition (PLD). The thickness of theouter conductive layer 103, as measured on the sidewalls of the trenches1103, may be in a range from 200 nm to 6 microns, although lesser andgreater thicknesses may also be employed. In an embodiment, thethickness of the outer conductive layer 103 may be in a range from 400nm to 3 microns. In another embodiment, the thickness of the outerconductive layer 103 may be in a range from 600 nm to 1.5 microns. Inanother embodiment, the thickness of the outer conductive layer 103 maybe in a range from 700 nm to 1 micron. A cavity 1103′ may be presentwithin each trench 1103 because the trenches 1103 are not completelyfilled by the outer conductive layer 103.

Subsequently, the outer conductive layer 103 may be patterned, forexample, by laser ablation. The pattern of the outer conductive layer103 may be selected to facilitate electrical wiring of photovoltaicdevices to be formed on the transparent sheet substrate 3710. Forexample, the outer conductive layer 103 may be patterned into aplurality of electrically isolated portions, each of which functions asan electrode of a photovoltaic device that may be connected in a seriesconnection and/or in a parallel connection.

Referring to FIG. 37C, a photovoltaic material layer (104, 105) may beformed on the surfaces of the outer conductive layer 103. The surfacesof the outer conductive layer 103 on which the photovoltaic materiallayer (104, 105) may be deposited include a planar top surface of theouter conductive layer 103 located above the moldable material layer3720, and inner sidewalls of the outer conductive layer 103 locatedinside the trenches 1103.

The photovoltaic material layer (104, 105) may include a second absorbersublayer 104 and a first absorber sublayer 105 as described above. Thephotovoltaic material layer (104, 105) may include a p-n junction or ap-i-n junction or a plurality of p-n junctions or p-i-n junctionsprovided that the photovoltaic material layer (104, 105) is a materialstack that generates and separates photogenerated electron-hole pairs inopposite directions, i.e., one of the electron and the hole toward theouter conductive layer 103 and the other of the electron and the holeaway from the outer conductive layer 103. The thickness of thephotovoltaic material layer (104, 105) may be in a range from 200 nm to6 microns, although lesser and greater thicknesses may also be employed.In an embodiment, the thickness of the photovoltaic material layer (104,105) may be in a range from 400 nm to 3 microns. In another embodiment,the thickness of the photovoltaic material layer (104, 105) may be in arange from 600 nm to 1.5 microns. In yet another embodiment, thethickness of the photovoltaic material layer (104, 105) may be in arange from 700 nm to 1 micron. The photovoltaic material layer (104,105) may be formed by low pressure chemical vapor deposition (LPCVD),physical vapor deposition (PVD), atomic layer deposition (ALD), or acombination thereof.

Subsequently, the photovoltaic material layer (104, 105) may bepatterned, for example, by laser ablation. The pattern of thephotovoltaic material layer (104, 105) may be selected to facilitateelectrical wiring of photovoltaic devices to be formed on thetransparent sheet substrate 3710. For example, the photovoltaic materiallayer (104, 105) may be patterned into a plurality of electricallyisolated portions. In an embodiment, a portion of the photovoltaicmaterial layer (104, 105) may be removed in a boundary region between aphotovoltaic region containing the photovoltaic bristles to be formedand a conducting trace region in which a current conducting trace for aportion of the outer conductor layer 103 is to be formed.

Referring to FIG. 37D, an optional transparent inner conductive layer107 a may be deposited by a conformal deposition method such as chemicalvapor deposition, or atomic layer deposition. Alternatively, theoptional transparent inner conductive layer 107 a may be deposited by anon-conformal deposition method such as physical vapor deposition. Theoptional transparent inner conductive layer 107 a may include atransparent conductive oxide material. In an embodiment, the transparentinner conductive layer 107 a includes aluminum doped zinc oxide(Al:ZnO). The thickness of the optional transparent inner conductivelayer 107 a, if present, may be in a range from 50 nm to 200 nm,although lesser and greater thicknesses may also be employed.

A conductive core layer 106 may be formed by deposition of a conductivematerial on the transparent inner conductive layer 107 a (if thetransparent inner conductive layer 107 a is present) or on thephotovoltaic material layer (104, 105) (if the transparent innerconductive layer 107 a is omitted). The conductive core layer 106 mayinclude the same material as the conductive cores 106 described above.The conductive core layer 106 may be a contiguous layer of a conductivematerial, and may be a metallic conductive layer, i.e., a conductivelayer composed of a metallic material. In an embodiment, the conductivecore layer 106 may include aluminum, copper, silver, gold, tungsten,nickel, cobalt, and/or any other conductive elemental metal. Further,the conductive core layer 106 may include an alloy of at least twoelemental metals and/or a stack of at least two metallic layers eachincluding an elemental metal or an alloy of at least two elementalmetals. In an embodiment, the conductive core layer 106 may include astack of a silver layer that contacts the transparent inner conductivelayer 107 a or the photovoltaic material layer (104, 105), and analuminum layer. The thickness of the conductive core layer 106, asmeasured on the sidewalls of the transparent inner conductive layer 107a or the photovoltaic material layer (104, 105) may be in a range from300 nm to 6 microns. In an embodiment, the thickness of the conductivecore layer 106 may be in a range from 500 nm to 3 microns. In anotherembodiment, the thickness of the conductive core layer 106 may be in arange from 750 nm to 1.5 microns. The conductive core layer 106 includesa core portion of each photovoltaic bristle formed in a respectivetrench 1103. The core portions of the photovoltaic bristles areelectrically shorted together because the conductive core layer 106 is acontiguous material layer.

The conductive core layer 106 may include the same material as the cores106 described above. The conductive core layer 106 (and the cores 106described above) may include a reflective metallic material, or atransparent material. The thickness of the conductive core layer 106 maybe in a range from 30 nm to 2,000 nm, although lesser and greaterthicknesses may also be employed.

In an embodiment, the conductive core layer 106 may include a metallicmaterial such as an elemental metal (e.g., aluminum, tungsten, copper,silver, gold, platinum, nickel, cobalt, chromium, titanium, tantalum,rhodium, iridium, zinc, and vanadium), an intermetallic alloy of atleast two elemental metals (e.g., the elemental metals listed above), aconductive metallic nitride (e.g., TiN, TaN, WN), a metal-semiconductoralloy (e.g., a metal silicide, and a metal germanosilicide), and/or acombination or a stack thereof. In an embodiment, the conductive corelayer 106 may include an optional diffusion barrier metallic liner suchas a conductive metallic nitride and a high conductivity material suchas an elemental metal. In an embodiment, the high conductivity materialmay be aluminum or copper.

In an embodiment, the conductive core layer 106 may employ a transparentconductive material that allows transmission of ambient light from thebackside of a photovoltaic device to the photovoltaic material layer(104, 105). The backside of the photovoltaic device corresponds to theupside of the exemplary in-process photovoltaic structure of FIG. 37D.While the backside efficiency of the photovoltaic structure may be lowerthan the efficiency of the proper side (front side) of the photovoltaicstructure due to higher intensity of radiation available from the frontside, an additional gain in efficiency may be realized through the useof a transparent conductive material. Exemplary transparent conductivematerials that may be employed for the conductive core layer 106include, but are not limited to, boron doped zinc oxide and aluminumdoped zinc oxide. In this case, the thickness of the transparentconductive core layer 106 may be in a range from 200 nm to 1,200 nm toprovide a highly conductive path to the tip of each photovoltaic brushwhile allowing light to pass through the transparent conductive corelayer 106.

The conductive core layer 106 may be formed by sputtering (physicalvapor deposition), chemical vapor deposition, or atomic layerdeposition. The thickness of the conductive core layer 106 may beselected such that the trenches 1103 are completely filled, or may beselected such that a via cavity 3769 is present within, or over, eachtrench 1103. As used herein, a via cavity 3769 refers to an unfilledvolume (i.e., a volume that is not occupied by any liquid or solid) thatextends most along a vertical direction. In other words, the maximumdimension of a via cavity may occur along the vertical direction. In anembodiment, the maximum vertical dimension of each via cavity 3769 maybe greater than the maximum lateral dimension of the via cavity 3769.The via cavity 3769 may be formed through many mechanisms.

In an embodiment, the via cavities 3769 may be formed when the amount ofthe deposited material for the conductive core layer 106 is insufficientto fill the trenches 1103. In this case, the cavities 1103′ within thetrenches 1103 do not disappear even after the conductive core layer 106is formed, and each remaining cavity 1103′ constitutes a via cavity3769. Such via cavities may also be present in the exemplary structuresof FIGS. 13I-13L and 15G-15J. The top surface of the conductive corelayer 106 includes a planar surface located within a horizontal plane(i.e., a Euclidean plane that is parallel to the top surface of thesheet substrate 3710) and inner sidewalls of the conductive core layer106 that extend into the trenches 1103 and define the lateral boundariesof the via cavities 3769.

Subsequently, the conductive core layer 106 and the optional transparentinner conductive layer 107 a may be patterned, for example, by laserablation. The pattern of remaining stacks of the conductive core layer106 and the optional transparent inner conductive layer 107 a may beselected to facilitate electrical wiring of photovoltaic devices to beformed on the transparent sheet substrate 3710. For example, theconductive core layer 106 and the optional transparent inner conductivelayer 107 a may be patterned into a plurality of electrically isolatedportions. In an embodiment, a portion of the conductive core layer 106and the optional transparent inner conductive layer 107 a may be removedin a boundary region between a photovoltaic region containingphotovoltaic bristles and a conducting trace region in which a currentconducting trace 1703 for the outer conductor layer 103 is formed.

Referring to FIG. 37E, a passivation substrate 3770 may be disposed onthe conductive core layer 106. In an embodiment, the bottom surface ofthe passivation substrate 3770 may contact the horizontal portion of thetop surface of the conductive core layer 106. As used herein, apassivation substrate refers to a substrate that passivates a structurethat it contacts, e.g., by protecting the structure from exposure to airor ambient conditions. In an embodiment, the passivation substrate 3770may include glass, sapphire, plastics, or other inert materials that donot interact with the material of the conductive core layer 106. In anembodiment, the passivation substrate 3770 may have a thickness in arange from 100 microns to 1 cm, although lesser and greater thicknessesmay also be employed. In an embodiment, the plurality of via cavities3769 may be filled with a gas, or may be in vacuum upon disposition ofthe passivation substrate 3770.

The outer conductive layer 103, the photovoltaic layer (104, 105), theoptional transparent inner conductive layer 107 a, and the conductivecore layer 106 collectively constitutes a photovoltaic layer stack 3700.The first exemplary photovoltaic structure may be flipped upside downsuch that a source of radiation (e.g., the sun) may be located withinthe upper hemisphere, which is defined as the space located above thehorizontal interface between the passivation substrate 3770 and thephotovoltaic layer stack 3700 after flipping of the first exemplaryphotovoltaic structure.

Referring to FIG. 37F, a magnified vertical cross-sectional view of aportion of the first exemplary photovoltaic structure of FIG. 37E afterflipping upside down is shown. A via cavity 3769 may be laterallybounded by a non-planar bottom surface of the conductive core layer 106,and may be vertically bounded by a top surface of the passivationsubstrate 3770, which is located within the same horizontal plane as theinterface between the conductive core layer 106 and the passivationsubstrate 3770.

Referring to FIG. 37G, a magnified vertical cross-sectional view of aportion of another embodiment of the first exemplary photovoltaicstructure is shown. The bottommost portion of each trench 1103 as formedat the processing step of FIG. 37A, i.e., the topmost portion of eachbristle as formed at the processing steps of FIG. 37E, may have arounded tip. In this case, each bristle may include a frustum portion3780 and a hemi-spheroid portion 3790. The hemi-spheroid portion 3790may have a shape that is approximately a hemi-spheroid, i.e., about onehalf of a spheroid. The ratio of the frustum height h1 to the height hof the bristle (3789, 3790) may be in a range from 0.7 to 0.95, althoughlesser and greater ratios may also be employed. In an embodiment, theratio of the frustum height h1 to the height h of the bristle (3789,3790) may be in a range from 0.76 to 0.90. In another embodiment, theratio of the frustum height h1 to the height h of the bristle (3789,3790) may be in a range from 0.80 to 0.87.

Referring to FIG. 37H, a perspective view of the first exemplaryphotovoltaic structure of FIG. 37E is illustrated, in which thetransparent sheet substrate 3710, the moldable material layer 3720(which is an optically transparent layer), and the passivation substrate3770 are illustrated with dotted lines to clearly illustrate the shapesof the photovoltaic bristles embedded within the photovoltaic layerstack 3700. While cylindrical shapes are illustrated for thephotovoltaic bristles, frustum shapes may also be employed for thephotovoltaic bristles.

As discussed above, the bristles may be arranged in a two-dimensionalhexagonal array. A center-to-center dimension ccd may be in a range from0.5 micron to 25 microns. The center-to-center dimension ccd refers tothe lateral distance between the a vertical axis passing through ageometrical center of a bristle (i.e., the geometrical center of thevolume of the bristle) and a vertical axis passing through a geometricalcenter of a nearest neighbor bristle. If the bristles have a cylindricalsymmetry, the center-to-center dimension ccd may be the lateral distancebetween a vertical symmetry axis of a bristle and a vertical symmetryaxis of a nearest neighbor bristle. In an embodiment, the ratio betweenthe base lateral dimension bd to the center-to-center dimension ccd maybe in a range from 0.75 to 0.99. In another embodiment, the ratiobetween the base lateral dimension bd to the center-to-center dimensionccd may be in a range from 0.85 to 0.97. In yet another embodiment, theratio between the base lateral dimension bd to the center-to-centerdimension ccd may be in a range from 0.92 to 0.96. In an embodiment, thecenter-to-center dimension ccd may be in a range from 1.1 micron to 12microns. In another embodiment, the center-to-center dimension ccd maybe in a range from 2.2 microns to 10 microns. In yet another embodiment,the center-to-center dimension ccd may be in a range from 4.4 microns to8.8 microns. In still another embodiment, the center-to-center dimensionccd may be in a range from 5.5 microns to 7.7 microns.

Referring to FIG. 37I, an alternative embodiment of the first exemplaryphotovoltaic structure of FIG. 37E is illustrated. One mechanism thatforms the via cavity 3769 is when the deposition method that depositsthe conductive core layer 106 is not sufficiently conformal, therebydepositing more material on the horizontal surfaces of the photovoltaicmaterial layer (104, 105) at the processing step of FIG. 37D than on thenon-horizontal sidewalls of the photovoltaic material layer (104, 105)within the trenches 1103. In this case, each via cavity 3769 may bedefined by a contiguous surface of the conductive core layer 106 thatdoes not touch (i.e., is spatially spaced from) the interface betweenthe conductive core layer 106 and the photovoltaic material layer (104,105) and does not touch the interface between the conductive core layer106 and the passivation substrate 3720.

Referring to FIG. 37J, an alternate embodiment of the first exemplaryphotovoltaic structure of FIG. 37E is illustrated. The process thatforms the conductive core layer 106 may be a conformal depositionprocess and the thickness of the deposited material may be sufficient tocompletely fill each trench 1103. In this case, a dimple may be formeddirectly over each trench 1103 by the top surface of the conductive corelayer 106 at the processing step of FIG. 37D. In this case, each viacavity 3769 may be defined by a non-planar portion of the top surface ofthe conductive core layer 106 at the processing step of FIG. 37D (or thebottom surface of the conductive core layer 106 as shown in FIG. 37J)and a portion of the horizontal surface of the passivation substrate3770 that contacts the conductive core layer 106. A seam 3779 may bepresent through the center of each trench 1103. In an embodiment, eachseam 3779 of the core conductive material layer 106 may extendvertically from an apex of each of the plurality of via cavities 3769.

Referring to FIG. 37K, a magnified vertical cross-sectional view ofanother embodiment of the first exemplary photovoltaic structure isillustrated. In this embodiment, a via cavity 3769 may not be formedwithin a photovoltaic bristle, and a seam 3779 extending along aone-dimensional line (in case the photovoltaic bristle has a cylindricalsymmetry) or along a vertical plane (in case the photovoltaic bristlehas a non-circular elliptical horizontal cross-sectional shape) may bepresent within each photovoltaic bristle.

Referring to FIG. 37L, a magnified vertical cross-sectional view offurther another embodiment of the first exemplary photovoltaic structureis illustrated. In this embodiment, the conductive core layer 106 mayinclude a transparent conductive material such as a transparentconductive oxide (TCO). In an embodiment, an optional inner transparentconductive layer 107 a may also be deposited in the structure before theconductive core layer 106, such as by sputtering or chemical vapordeposition. The transparent conductive material of the conductive corelayer 106 may be deposited, for example, by sputtering or chemical vapordeposition. A via cavity 3769 that is entirely laterally surrounded by asurface of the conductive core layer 106, including the transparentconductive material may be present within each photovoltaic bristle. Inthis case, backside illumination, which refers to radiation enteringthrough the passivation substrate 3770, may contribute to additionalphotogeneration of electricity from each photovoltaic bristle. Thepassivation substrate 3770 may include a transparent material such asglass or sapphire.

Referring to FIG. 37M, a magnified vertical cross-sectional view ofanother embodiment of the first exemplary photovoltaic structure isillustrated. The optional inner transparent conductive layer 107 a inthe structure illustrated in FIG. 36L may be omitted to form thestructure illustrated in FIG. 37M.

Referring to FIG. 37N, a magnified vertical cross-sectional view ofanother embodiment of the first exemplary photovoltaic structure isillustrated. If the conformity of the deposition process employed todeposit the conductive core layer 106 is high enough, a seam 3779 may beformed within each photovoltaic bristle, and a via cavity 3769 may beformed below the horizontal plane including the bottommost surface ofthe photovoltaic material layer (104, 105).

Referring to FIG. 38A, a second exemplary in-process photovoltaicstructure is illustrated, which may include a moldable material layer3820 that is provided as a substrate and includes an imprint pattern.The imprint pattern may be the same as the imprint pattern of the firstexemplary in-process photovoltaic structure of FIG. 37A. The moldablematerial of the moldable material layer 3820 may be an opticallytransparent material that is transparent within a visible wavelengthrange. The moldable material layer 3820 may be provided in a form havinga sufficient mechanical strength to be handled manually or withmechanical devices. The moldable material layer 3820 may be a moldablesubstrate including a moldable material and having a thickness t in arange from 5 microns to 5 mm, although lesser and greater thicknessesmay also be employed. As such, the moldable material layer 3820 may bethe final substrate 3609 d as provided by the processing steps of FIG.36A. Alternatively, the moldable material layer 3820 may be provided ona substrate of another material.

In an embodiment, the moldable material layer 3820 may include amoldable substrate that includes a glass transition material. As usedherein, a “glass transition material” is a material that displays thebehavior of glass transition. A “glass transition” refers to atransition from a liquid to a solid-like state that occurs duringcooling or compression in which viscosity increases by at least oneorder of magnitude. Thermal expansion coefficient, heat capacity, shearmodulus, and many other properties of inorganic glasses show arelatively sudden change at the glass transition temperature. Any suchstep or kink may be used to define the glass transition temperature.Glass transition materials include, among others, plastics, resins, andglass materials based on silica.

Silica and many other polymer materials exhibit glass transition. In anembodiment, the glass transition material may be selected fromterephthalate (PET), polypropylene (PP), polyethylene (PE), nylon,polyoxymethylene (POM), polybutylene terephthalate (PBT),polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVFD),polyethylenechlorotrifluoroethylene (PECTFE), polyethylenetetrafluoroethylene (PETFE), polycarbonate (PC), polymethylmethacrylate(PMMA), polymethacrylate (PMA), cyclic polyolefin, methylmethylacrylicacid, hydroxyethylmethylmethacrylate, fluorofunctinoalizedmethylmethacrylate, silicone-functionalized methylmethacrylate,soda-lime-silica glass, borophosphosilicate glass, and phosphosilicateglass.

In an embodiment, the glass transition material of the moldable materiallayer 3820 may be a plastic material prepared from semicrystalline oramorphous polymer resins such as polyethylene terephthalate (PET),polypropylene (PP), high density polyethylene (HDPE), low densitypolyethylene (LDPE), nylon, polyoxymethylene (POM), polybutyleneterephthalate (PBT), polytetrafluoroethylene (PTFE), polyvinylidenefluoride (PVFD), polyethylenechlorotrifluoroethylene (PECTFE),polyethylene tetrafluoroethylene (PETFE), similar fluoro-based andnon-fluoro-based polymers blended together or copolymerized in one ormore mixtures, polycarbonate (PC), polymethylmethacrylate (PMMA),polymethacrylate (PMA), cyclic polyolefin (branded under the trade nameTopas™), and similar polymers blended together or copolymerized in oneor more mixtures.

In an embodiment, the glass transition material of the moldable materiallayer 3820 may be any of the resin material that may be employed for themoldable material layer 3720 as described above.

In an embodiment, the glass transition material of the moldable materiallayer 3820 may be a glass-based on silica (SiO₂) blended with othernon-silicate glasses or elements. Examples of silica-based glassesinclude, but are not limited, to soda-lime glass, borosilicate glass,and borophosphatesilicate glass or similar materials. In an embodiment,the glass transition material may be soda-lime glass.

A web-to-plate system 3500 of FIG. 35A may be adapted to process anunpatterned moldable material layer 3820 to provide an imprintedpattern. Referring to FIG. 39, a web-to-plate system 3900 isillustrated, which is a modification of the web-to-plate system 3500 ofFIG. 35A to provide additional processing capabilities if the moldablematerial layer 3820 is provided as a moldable substrate including aglass transition material, or as a moldable material layer of a glasstransition material provided on another substrate.

If the moldable material layer 3820 is provided as a moldable substrateor on another substrate, a moldable material applicator 3612 illustratedin FIG. 35A is not necessary. Instead of a moldable material applicator3612, a pre-treatment device 3980 that may provide a suitable level ofviscosity to the moldable material layer 3820 may be provided in thepath of transit for a pre-imprint substrate 3820 a (which is a moldablematerial layer 3820 or a combination of a moldable material layer 3820and a substrate) prior to imprinting. In an embodiment, thepre-treatment device 3980 may be a temperature control device such as aheater or a refrigerator. Depending on the viscosity of the moldablematerial layer 3820 in the pre-imprint substrate 3820 a, thepre-treatment device 3980 may harden (increase the viscosity of) orsoften (decrease the viscosity of) the moldable material of the moldablematerial layer 380.

In an embodiment, the pre-treatment device 3980 may be a heaterconfigured to heat the top side of the pre-imprint substrate 3820 a(which may be a moldable substrate) during transportation to the imprintlocation. The amount of the heat transferred from the pre-treatmentdevice 3980 to the pre-implant substrate 3820 a may be controlled suchthat the top surface of the pre-implant substrate 3820 has a suitablelevel of viscosity. The temperature of the top surface of thepre-implant substrate 3820 at the time of imprinting may be at, above,or below the glass transition temperature of the glass transitionmaterial of the moldable material layer 3820 as provided within thepre-implant substrate 3820 a.

In an embodiment, the temperature of the linear drive mechanism 3610(such as rollers) may be controlled to provide a lower temperature tothe backside of the pre-imprint substrate 3810 a to prevent a lowerlevel of viscosity than the front side of the pre-imprint substrate3820, and thus, prevent sticking of the pre-imprint substrate 3820 a tothe linear drive mechanism 3610. The backside of the pre-imprintsubstrate 3820 a may be cooled during transportation to the imprintlocation (the location of the transfer gap roller 3607). In anillustrative example, the cooling of the linear drive mechanism 3610 maybe effected by air cooling effected, for example, by a first fan 3971,or may be effected by a refrigeration system or a cooling system thatcools the linear drive mechanism 3610 in any other manner.

The imprinted substrate 3820 c may be temperature cooled to prevent lossof the imprinted pattern due to excessive viscous flow of the moldablematerial layer 3820 within the imprinted substrate 3820 c. For example,a second fan 3972 may be employed to circulate air over the imprintedsubstrate 3820 c and to provide cooling of the imprinted substrate 3820c in case cooling of the imprinted substrate 3820 c is desired to reducethe viscosity. In an embodiment, a refrigerated air may be circulated bythe second fan 3972. In this case, the imprinted substrate 3820 c may beplaced in a mini-environment to reduce the cost of cooling a largespace.

In case the top surface of the pre-imprint substrate 3810 a is heatedprior to imprinting, the die as incorporated into the web (such as adaughter die web 3501 d) may be cooled after imprinting, i.e., aftertransfer of the pattern of the die into the moldable material layer3820, to minimize damage to the web. Optionally, a third fan 3973 may beemployed to cool the web before the web is wound into a roll.

The imprinted substrate 3820 c may be further subjected to an optionaldensification or rigidification process. For example, a densificationdevice 3990 may be employed to increase the viscosity of the moldablematerial layer 3820 in the imprinted substrate 3820 c to provide a finalsubstrate 3820 d, which may be employed to perform the processing stepof FIG. 38B thereupon. The densification device 3990 may use anysuitable mechanism that increases the viscosity and/or rigidity of themoldable material layer 3820, for example, by providing heat, cold,moisture, agitation, application of a catalyst, irradiation by visiblelight, ultraviolet light, or infrared light, ventilation, or acombination thereof.

Referring to FIG. 38B, an outer conductive layer 103 may be formed onthe moldable material layer 3820 (as provided within a finishedsubstrate 3820 d) by performing the processing steps of FIG. 37B.

Referring to FIG. 38C, a photovoltaic material layer (104, 105) may beformed on the upper surface of the outer conductive layer 103 byperforming the processing steps of FIG. 37C.

Referring to FIG. 38D, an optional transparent inner conductive layer107 a and a conductive core layer 106 may be on the upper surface of thephotovoltaic material layer (104, 105) by performing the processingsteps of FIG. 37D. Via cavities 3769 and/or seams 3779 may be formed inthe same manner as illustrated in FIGS. 37F, 37G, 37I, and 37J. Theplurality of via cavities 3769 may be filled with a gas, or may be invacuum depending on the ambient conditions at the time of disposing thepassivation substrate 3770.

Referring to FIG. 38E, a passivation substrate 3770 may be disposed onthe conductive core layer 106 to seal the conductive core layer 106 inthe same manner as in the case of the first exemplary photovoltaicstructure illustrated in FIG. 37E. A second exemplary photovoltaicstructure is formed, which is illustrated in a perspective view in FIG.38F.

Each of the photovoltaic structures illustrated in FIGS. 37E-37J, 38E,and 38F includes a layer stack 3700 located over a substrate 3770 andincludes a core conductive material layer 106, a photovoltaic materiallayer (105, 104), and a transparent conductive material layer 103. Aplurality of via cavities 3769 may be located underneath verticallyprotruding portions of the layer stack 3700 (which form photovoltaicbristles) and above the substrate 3770 and may be free of any solidphase material therein.

The passivation substrate 3770 having a planar bottom surface may bedisposed directly on a physically exposed planar surface of the coreconductive material layer 106. A plurality of via cavities 3769 may belaterally surrounded by the core conductive material layer 106, and maybe vertically bounded by the passivation substrate 3770. In anembodiment, each of the plurality of via cavities 3769 may be athree-dimensional closed shape defined by a portion of a planar surfaceof the substrate 3770 and a non-planar portion of a contiguous surfaceof the core conductive material layer 106.

The contiguous surface of the core conductive material layer 106 may bethe bottom surface of the core conductive material layer 106 in theupright position (as illustrated in FIGS. 37F-37J and 38F), and is a topsurface of the core conductive material layer 106 prior to flipping thephotovoltaic structures (as illustrated in FIGS. 37D, 37E, 38D, and38E). The contiguous surface of the core conductive material layer 106may be located within the same horizontal plane as the top surface ofthe substrate 3770 when the photovoltaic structure is in the uprightposition.

The three-dimensional closed shape may have a variable horizontalcross-sectional area that decreases strictly with a vertical distancefrom a top surface of the substrate 3770 as illustrated in FIG. 37F,37G, and FIG. 37J. Alternatively, the three-dimensional closed shape mayhave a variable horizontal cross-sectional area that has a maximum at acertain vertical distance from a top surface of the substrate 3770 asillustrated in FIG. 37I. In an embodiment, the three-dimensional closedshape of a via cavity 3769 may be a conical shape. In an embodiment, aseam of the core conductive material layer 106 may extend upwardvertically from a topmost apex of each of the plurality of via cavities3769 as illustrated in FIG. 37J.

The moldable material layer (3720, 3820) may be located on the layerstack 3700, and may overlie the layer stack 3700 in the uprightorientation. The moldable material layer (3720, 3820) may be anoptically transparent layer, and the entirety of the top surface of themoldable material layer (3720, 3820) may be planar in the uprightorientation. The moldable material layer (3720, 3820) may include anoptically transparent material selected from a material selected from alacquer, a silicone precursor material, a gel derived from a sol, and aglass transition material. In an embodiment, the optically transparentmaterial may be selected from phenylalkyl catechol-based lacquers,nitrocellulose lacquers, acrylic lacquers, and water-based lacquers. Inanother embodiment, the optically transparent material may includesilicone. In another embodiment, the optically transparent material maybe selected from a gel of silicon oxide and a gel of dielectric metaloxide.

In another embodiment, the optically transparent material may be a glasstransition material selected from terephthalate (PET), polypropylene(PP), polyethylene (PE), nylon, polyoxymethylene (POM), polybutyleneterephthalate (PBT), polytetrafluoroethylene (PTFE), polyvinylidenefluoride (PVFD), polyethylenechlorotrifluoroethylene (PECTFE),polyethylene tetrafluoroethylene (PETFE), polycarbonate (PC),polymethylmethacrylate (PMMA), polymethacrylate (PMA), cyclicpolyolefin, methylmethylacrylic acid, hydroxyethylmethylmethacrylate,fluorofunctinoalized methylmethacrylate, silicone-functionalizedmethylmethacrylate, soda-lime-silica glass, borophosphosilicate glass,and phosphosilicate glass.

The moldable material layer (3720, 3820) may be a transparent dielectriclayer. The moldable material layer (3720, 3820) may contact a topsurface of the transparent conductive layer 103, and may have a topsurface having a uniform vertical distance from a horizontal interfacebetween the passivation substrate 3770 and the core conductive materiallayer 106. The top surface of the moldable material layer (3720, 3820)may be located above a horizontal plane including topmost surfaces ofthe transparent conductive material layer 103, i.e., the horizontalplane including the topmost surfaces of the photovoltaic bristles.

Each of the exemplary structures of FIGS. 37D-37N and 38D-38F illustratea portion of a metamaterial including an array of photovoltaic bristleshaving approximately cylindrical shapes. As used herein, an“approximately cylindrical shape” refers to a shape that istopologically homeomorphic to a cylinder of a circular or polygonalhorizontal cross-sectional shape and having sidewalls that are verticalor having a taper angle less than 10 degrees. The top portion of an“approximately cylindrical shape” may be pointed, or may be rounded.

The metamaterial may be formed by forming an array of vias 1103extending into a substrate, which may be a combination of a sheetsubstrate 3710 and a moldable material layer 3720 as illustrated in FIG.37A, or may be a moldable material layer 3820 as illustrated in FIG.38A. Each via 1103 within the array has an approximately cylindricalshape and is laterally separated from one another, and is laterallysurrounded, by the substrate ((3710, 3720); 3820). In one embodiment,the moldable material layer (3720, 3820) may be patterned by imprintinga die including a pattern of protruding structures and incorporated intoa web onto the moldable material layer (3720, 3820). The patternedmoldable material layer (3720, 3820) includes a pattern of via cavities.The patterned moldable material layer (3720, 3820) is subsequently curedto form a rigid structure.

A transparent conductive layer 103 (i.e., an outer conductive layer 103)is formed over the array of vias 1103. An absorber layer (104, 105) isformed over the outer conductive layer 103. A core conductive materiallayer 106 (i.e., the conductive core layer 106 or the core 106) isformed over the absorber layer (104, 105). Each via 1103 is partiallyfilled with the core conductive material layer 106 to form a conductivecore of a respective photovoltaic bristle. A base layer 3770 (which maybe a passivation substrate 3770) is formed over the deposited conductivematerial. A non-solid core 3769 (i.e., a via cavity 3769) that does notinclude the conductive material or a material of the base layer 3770 isformed within each photovoltaic bristle and between the core conductivematerial layer 106 and the base layer 3770.

In one embodiment, the substrate ((3710, 3720); 3820) comprises amoldable material. Formation of the array of vias 1103 may be iseffected by moving the moldable material under a rolling press or undera rolling die that transfers a pattern thereupon on the moldablematerial. The conductive cores 106 of photovoltaic bristles and the coreconductive material layer 106 may be formed as a single contiguousstructure in a same deposition process. The transparent conductive layer103 may comprise transparent conductive oxide or transparent conductivenitride. In one embodiment, the passivation substrate 3770 may comprisea non-conductive transparent layer disposed over the array of vias 1103.In one embodiment, the substrate ((3710, 3720); 3820) comprises apolymer. For example, the substrate ((3710, 3720); 3820) may include amoldable material layer (3720, 3820) comprising a polymer.

Referring to FIG. 40, a system 4100 for manufacturing a photovoltaicstructure may include a web-to-plate system (3600, 3900) such as thesystem illustrated in FIG. 36A, and a deposition system 4000 including aplurality of process chambers (4010, 4020, 4030, 4040, 4050, 4060). Theweb-to-plate system (3600, 3900) may be configured to imprint a die(e.g., a daughter die web 3501 d in FIG. 36A) including a pattern ofprotruding structures onto a moldable material layer 3720 (which is thecoating layer in a coated substrate 3509 b in FIG. 36A) to generate apattern of trenches 1103 extending downward from a top surface of themoldable material layer 3720. The die may be incorporated into a web asin the case of the daughter die web 3501 d. A roll-to-web system 3500,as illustrated in FIG. 35A, may be employed to provide a web with animprint pattern to the web-to-plate system (3600, 3900).

In an embodiment, the web-to-plate system (3600, 3900) may include amoldable material dispensation subsystem including a moldable materialcontainer (such as the container containing the moldable material 3613illustrated in FIG. 36A) and a moldable material dispenser (such as thesecond moldable material applicator 3612 illustrated in FIG. 36A). Themoldable material dispenser may be configured to coat the moldablematerial layer 3720 on a sheet substrate 3710 prior to transportation ofthe sheet substrate 3710 to an imprint location. The moldable materialmay be selected from a lacquer, a silicone precursor material, a gelderived from a sol, and a glass transition material as described above.In case a sol-gel material is employed for the moldable material layer(3720, 3820), a sol may be applied onto the sheet substrate 3710, andtransition of the sol into a gel may be induced to form the moldablematerial layer 3720. In an embodiment, the moldable material layer 3720may be selected from a gel of silicon oxide and a gel of dielectricmetal oxide. The moldable material layer 3720 may include an opticallytransparent material that is transparent within the visible wavelengthrange.

Optionally, the web-to-plate system (3600, 3900) may further include adensification device configured to reduce elasticity of the moldablematerial prior to, or after, imprinting. For example, a curing mechanism3615 illustrated in FIG. 36A and/or a densification device 3990 and/or asecond fan 3972 illustrated in FIG. 39 may be employed. In anembodiment, the densification device may include at least one of a fan,a heater, an ultraviolet treatment system, an agitator, and a laserirradiation system.

In an embodiment, the moldable material layer 3820 may be a moldablesubstrate including a glass transition material, and the web-to-platesystem 3900 may include a moldable substrate transportation subsystem(such as the linear drive mechanism 3610) configured to transport themoldable substrate to an imprint location. The moldable material layer3820 may include an optically transparent material that is transparentwithin the visible wavelength range.

In an embodiment, the web-to-plate system 3900 may include a heatingsystem 3980 configured to heat a top side of the moldable substrateduring transportation to the imprint location. In an embodiment, theweb-to-plate system 3900 may include a substrate backside cooling system(such as the first fan 3971 or a built-in cooling system within thelinear drive mechanism 3600) configured to cool a backside of eachmoldable substrate during transportation to the imprint location. In anembodiment, a web cooling system (such as the third fan 3973 in FIG. 39)may be provided, which may be configured to cool the die after transferof the pattern of the die into the moldable material layer 3820.

A die including a pattern of protruding structures and incorporated intoa web may be imprinted onto the moldable material layer (3720, 3820).The patterned moldable material layer (3720, 3820) may be an opticallytransparent layer including the pattern of trenches 1103.

After the web-to-plate system (3600, 3900) forms a pattern of trenches1103 extending downward from a top surface of a moldable material layer(3720, 3820) (which may be an optically transparent layer), atransparent conductive material layer 103, a photovoltaic material layer(104, 105), and a core conductive material layer 106 may be sequentiallydeposited within the pattern of trenches 1103 in the moldable materiallayer (3720, 3820) as described above. A via cavity 3769 may be formedwithin, or above, each trench 1103. In an embodiment, the coreconductive material layer 106 may incompletely fill the trenches 1103.

The system 4100 for manufacturing the photovoltaic structure may furtherinclude a deposition system 4000 configured to sequentially deposit atransparent conductive material layer 103, a photovoltaic material layer(104, 105), and a core conductive material layer 106 within the patternof trenches 1103 in the moldable material layer (3720, 3820).

The plurality of process chambers (4010-4080) in the deposition system4000 may be integrated into an automated deposition system in which thein-process photovoltaic structure is processed step by step employing anintegrated robotic transport system or a manual transport system. Theplurality of process chambers (4010-4080) may include, for example, atransparent conductive layer deposition module 4010 that deposits atransparent conductive layer 103, a first laser scribing module 4020that patterns the transparent conductive layer 103, a first photovoltaicmaterial deposition module 4030 that deposits a first absorber sublayer104 of a first conductivity type, a second photovoltaic materialdeposition module 4040 that deposits a second absorber sublayer 105 of asecond conductivity type (which is the opposite of the firstconductivity type), a second laser scribing module 4050 that patternsthe first and second absorber sublayers (104, 105) (i.e., thephotovoltaic material layer (104, 105)), an optional transparent innerconductive layer deposition module 4060 that deposits a transparentinner conductive layer 107 a, a conductive core layer deposition module4070 that deposits a conductive core layer 106, and a third laserscribing module 4080 that patterns the conductive core layer 106 and theoptional transparent inner conductive layer 107 a. Optionally, assemblyof a passivation substrate 3770 may be automated employing anotherprocess module that processes the output substrate from the secondconductive trace module 4060.

Referring to FIG. 41A, a third exemplary structure according to anembodiment of the present disclosure may be derived from the firstexemplary structure illustrated in FIG. 37D. As discussed above, a topsurface of a moldable material layer 3720 may be patterned with an arraypattern. The array pattern includes an array of vertically extendingshapes that protrude downward from that top surface of the moldablematerial layer 3720, i.e., an array of via 1103 that includes viacavities therein. A layer stack (103, 014, 105, 107 a, 106) may beformed over the array pattern. The layer stack comprising a transparentconductive material layer 103, a photovoltaic material layer (104, 105),an optional transparent inner conductive layer 107 a, and a coreconductive material layer 106. Specifically, the transparent conductivematerial layer 103 is deposited on surfaces of the via cavities 1103 andthe top surface of the moldable material layer (3720, 3820), thephotovoltaic material layer (104, 105) is deposited on the transparentconductive material layer 103, and the core conductive material layer103 is deposited on the photovoltaic material layer (104, 105). Theconductive cores 106 of photovoltaic bristles and the core conductivematerial layer 106 may be formed as a single contiguous structure in asame deposition process. The transparent conductive layer 103 maycomprise transparent conductive oxide or transparent conductive nitride.

A dielectric material layer 4120 is deposited in each of the cavitiesthat overlying recessed portions (i.e., portions that protrude downward)of the core conductive material layer 106. The dielectric material layer4120 comprises a dielectric material, i.e., an electrical insulator),and may be deposited by a conformal deposited method (such as chemicalvapor deposition), a self-planarizing deposition method (such asspin-coating, spraying, immersion in a bath including the dielectricmaterial, etc. In one embodiment, each via cavity 1103 may be entirelyfilled with a respective photovoltaic bristle, which includes verticallyextending portions of the transparent conductive material layer 103, thephotovoltaic material layer (104, 105), the core conductive materiallayer 106, and the dielectric material layer 4120. Each verticallyextending portion of the dielectric material layer 4120 constitutes adielectric core 4122. Thus, each dielectric core 4122 may be a portionof the dielectric material layer 4120 that protrudes into a respectivevia cavity.

The polymer material that may be employed for the dielectric materiallayer 4120 may, or may not, be an optically transparent material.Non-limiting examples of the polymer material that may be employed forthe dielectric material layer 4120 include poly(hexafluoropropyleneoxide), hydroxypropyl cellulose,poly(tetrafluoroethylene-co-hexafluoropropylene),poly(pentadecafluorooctyl acrylate),poly(tetrafluoro-3-(heptafluoropropoxy)propyl acrylate),poly(tetrafluoro-3-(pentafluoroethoxy)propyl acrylate),poly(tetrafluoroethylene), poly(undecafluorohexyl acrylate),poly(nonafluoropentyl acrylate),poly(tetrafluoro-3-(trifluoromethoxy)propyl acrylate),poly(pentafluorovinyl propionate), poly(heptafluorobutyl acrylate),poly(trifluorovinyl acetate), poly(octafluoropentyl acrylate),poly(methyl 3,3,3-trifluoropropyl siloxane), poly(pentafluoropropylacrylate), poly(2-heptafluorobutoxy)ethyl acrylate),poly(chlorotrifluoroethylene), poly(2,2,3,4,4-hexafluorobutyl acrylate),poly(methyl hydro siloxane), poly(methacrylic acid), poly(dimethylsiloxane), poly(trifluoroethyl acrylate),poly(2-(1,1,2,2-tetrafluoroethoxy)ethyl acrylate,poly(trifluoroisopropyl methacrylate),poly(2,2,2-trifluoro-1-methylethyl methacrylate),poly(2-trifluoroethoxyethyl acrylate), poly(vinylidene fluoride),poly(trifluoroethyl methacrylate), poly(methyl octadecyl siloxane),poly(methyl hexyl siloxane), poly(methyl octyl siloxane), poly(isobutylmethacrylate), poly(vinyl isobutyl ether), poly(methyl hexadecylsiloxane), poly(ethylene oxide), poly(vinyl ethyl ether), poly(methyltetradecyl siloxane), poly(ethylene glycol mono-methyl ether),poly(vinyl n-butyl ether), polypropylene oxide), poly(3-butoxypropyleneoxide), poly(3-hexoxypropylene oxide), poly(ethylene glycol), poly(vinyln-pentyl ether), poly(vinyl n-hexyl ether),poly(4-fluoro-2-trifluoromethylstyrene), poly(vinyl octyl ether),poly(vinyl n-octyl acrylate), poly(vinyl 2-ethylhexyl ether), poly(vinyln-decyl ether), poly(2-methoxyethyl acrylate), poly(acryloxypropylmethyl siloxane), poly(4-methyl-1-pentene), poly(3-methoxypropyleneoxide), poly(t-butyl methacrylate), poly(vinyl n-dodecyl ether),poly(3-ethoxypropyl acrylate), poly(vinyl propionate), poly(vinylacetate), poly(vinyl propionate), poly(vinyl methyl ether), poly(ethylacrylate), poly(vinyl methyl ether) (isotactic), poly(3-methoxypropylacrylate), poly(l-octadecene), poly(2-ethoxyethyl acrylate),poly(isopropyl acrylate), poly(l-decene), poly(propylene), poly(laurylmethacrylate), poly(vinyl sec-butyl ether), poly(n-butyl acrylate),poly(dodecyl methacrylate), poly(ethylene succinate), poly(tetradecylmethacrylate), poly(hexadecyl methacrylate), cellulose acetate butyrate,cellulose acetate, poly(vinyl formate), poly(2-fluoroethylmethacrylate), poly(octyl methyl silane), ethyl cellulose, poly(methylacrylate), poly(dicyanopropyl siloxane), poly(oxymethylene),poly(sec-butyl methacrylate), poly(dimethylsiloxane-co-alpha-methylstyrene), poly(n-hexyl methacrylate), poly(n-butyl methacrylate),poly(ethylidene dimethacrylate), poly(2-ethoxyethyl methacrylate),poly(n-propyl methacrylate), poly(ethylene maleate), poly(ethylmethacrylate), poly(vinyl butyral), poly(3,3,5-trimethylcyclohexylmethacrylate), poly(2-nitro-2-methylpropyl methacrylate),poly(dimethylsiloxane-co-diphenylsiloxane), poly(1,1-diethylpropylmethacrylate), poly(triethylcarbinyl methacrylate), poly(methylmethacrylate), poly(2-decyl-1,4-butadiene), polypropylene, isotactic,poly(mercaptopropyl methyl siloxane), poly(ethyl glycolatemethacrylate), poly(3-methylcyclohexyl methacrylate), poly(cyclohexylalpha-ethoxyacrylate), methyl cellulose, poly(4-methylcyclohexylmethacrylate), poly(decamethylene glycol dimethacrylate), poly(vinylalcohol), poly(vinyl formal), poly(2-bromo-4-trifluoromethyl styrene),poly(1,2-butadiene), poly(sec-butyl alpha-chloroacrylate),poly(2-heptyl-1,4-butadiene), poly(vinyl methyl ketone), poly(ethylalpha-chloroacrylate), poly(vinyl formal),poly(2-isopropyl-1,4-butadiene), poly(2-methylcyclohexyl methacrylate),poly(bornyl methacrylate), poly(2-t-butyl-1,4-butadiene), poly(ethyleneglycol dimethacrylate), poly(cyclohexyl methacrylate),poly(cyclohexanediol-1,4-dimethacrylate), butyl rubber,poly(tetrahydrofurfuryl methacrylate), poly(isobutylene), polyethylene,cellulose nitrate, polyacetal, poly(l-methylcyclohexyl methacrylate),poly(2-hydroxyethyl methacrylate), poly(l-butene), poly(vinylmethacrylate), poly(vinyl chloroacetate), poly(N-butyl methacrylamide),Poly(2-chloroethyl methacrylate), poly(methyl alpha-chloroacrylate),poly(2-diethylaminoethyl methacrylate), poly(2-chlorocyclohexylmethacrylate), poly(1,4-butadiene) (35% cis; 56% trans; 7% 1,2-content),poly(acrylonitrile), poly(isoprene), poly(allyl methacrylate),poly(methacrylonitrile), poly(methyl isopropenyl ketone),poly(butadiene-co-acrylonitrile), poly(2-ethyl-2-oxazoline),poly(N-2-methoxyethyl)methacrylamide, poly(2,3-dimethylbutadiene),poly(2-chloro-1-(chloromethyl)ethyl methacrylate),poly(1,3-dichloropropyl methacrylate), poly(acrylic acid), poly(N-vinylpyrrolidone), nylon 6 [Poly(caprolactam)], poly(butadiene-co-styrene),poly(cyclohexyl alpha-chloroacrylate), poly(methyl phenyl siloxane),poly(2-chloroethyl alpha-chloroacrylate), poly(2-aminoethylmethacrylate), poly(furfuryl methacrylate), poly(vinyl chloride),poly(butylmercaptyl methacrylate), poly(1-phenyl-n-amyl methacrylate),poly(N-methyl methacrylamide), polyethylene, cellulose, poly(cyclohexylalpha-bromoacrylate), poly(sec-butyl alpha-bromoacrylate),poly(2-bromoethyl methacrylate), poly(dihydroabietic acid), poly(abieticacid), poly(ethylmercaptyl methacrylate), poly(N-allyl methacrylamide),poly(1-phenylethyl methacrylate), poly(2-vinyltetrahydrofuran),poly(vinylfuran), poly(methyl m-chlorophenylethyl siloxane),poly(p-methoxybenzyl methacrylate), poly(isopropyl methacrylate),poly(p-isopropyl styrene), poly(isoprene), poly(p,p′-xylylenyldimethacrylate), poly(cyclohexyl methyl silane), poly(1-phenylallylmethacrylate), poly(p-cyclohexylphenyl methacrylate), poly(chloroprene),poly(2-phenylethyl methacrylate), poly(methyl m-chlorophenyl siloxane),poly[4,4-heptane bis(4-phenyl)carbonate)], poly[1-(o-chlorophenyl)ethylmethacrylate)], styrene/maleic anhydride copolymer,poly(1-phenylcyclohexyl methacrylate), nylon 6,10 [poly(hexamethylenesebacamide)], nylon 6,6 [poly(hexamethylene adipamide)], nylon 6(3)T[poly(trimethyl hexamethylene terephthalamide)],poly(2,2,2′-trimethylhexamethylene terephthalamide), poly(methylalpha-bromoacrylate), poly(benzyl methacrylate),poly[2-(phenylsulfonyl)ethyl methacrylate], poly(m-cresyl methacrylate),styrene/acrylonitrile copolymer, poly(o-methoxyphenol methacrylate),poly(phenyl methacrylate), poly(o-cresyl methacrylate), poly(diallylphthalate), poly(2,3-dibromopropyl methacrylate),poly(2,6-dimethyl-p-phenylene oxide), poly(ethylene terephthalate),poly(vinyl benozoate), poly[2,2-propanebis[4-(2-methylphenyl)]carbonate], poly[1,1-butanebis(4-phenyl)carbonate], poly(1,2-diphenylethyl methacrylate),poly(o-chlorobenzyl methacrylate), poly(m-nitrobenzyl methacrylate).poly(oxycarbonyloxy-1,4-phenyleneisopropylidene-1,4-phenylene),poly[N-(2-phenylethyl)methacrylamide], poly(1,1-cyclohexanebis[4-(2,6-dichlorophenyl)]carbonate], polycarbonate resin, bisphenol-Apolycarbonate, poly(4-methoxy-2-methylstyrene), poly(o-methyl styrene),polystyrene, poly[2,2-propane bis[4-(2-chlorophenyl)]carbonate],poly[1,1-cyclohexane bis(4-phenyl)carbonate], poly(o-methoxy styrene),poly(diphenylmethyl methacrylate), poly[1,1-ethanebis(4-phenyl)carbonate], poly(propylene sulfide), poly(p-bromophenylmethacrylate), poly(N-benzyl methacrylamide), poly(p-methoxy styrene),poly(4-methoxystyrene), poly[1,1-cyclopentane bis(4-phenyl)carbonate],poly(vinylidene chloride), poly(o-chlorodiphenylmethyl methacrylate),poly[2,2-propane bis[4-(2,6-dichlorophenyl)]carbonate],poly(pentachlorophenyl methacrylate), poly(2-chlorostyrene),poly(alpha-methylstyrene), poly(phenyl alpha-bromoacrylate),poly[2,2-propane bis[4-(2,6-dibromophenyl)cabonate],poly(p-divinylbenzene), poly(N-vinyl phthalimide),poly(2,6-dichlorostyrene), poly(chloro-p-xylene), poly(beta-naphthylmethacrylate), poly(alpha-naphthyl carbinyl methacrylate), poly(phenylmethyl silane), poly(sulfone) [Poly[4,4′-isopropylidene diphenoxydi(4-phenylene)sulfone]], polysulfone resin, poly(2-vinylthiophene),poly(2,6-diphenyl-1,4-phenylene oxide), poly(alpha-naphthylmethacrylate), poly(p-phenylene ether-sulphone), poly[diphenylmethanebis(4-phenyl)carbonate], poly(vinyl phenyl sulfide), poly(styrenesulfide), butylphenol formaldehyde resin, polyp-xylylene),poly(2-vinylnaphthalene), poly(N-vinyl carbazole),naphthalene-formaldehyde rubber, phenol-formaldehyde resin, andpoly(pentabromophenyl methacrylate). In one embodiment, the dielectricmaterial layer 4120 may include ethylene vinyl acetate.

In one embodiment, the thickness of the deposited dielectric material ofthe dielectric material layer 4120 may be selected such that allunfilled volumes of the via cavities 1103 are filled with the dielectricmaterial of the dielectric material layer 4120. For example, thethickness of the dielectric material layer 4120 as measured over atopmost surface of the core conductive material layer 107 may be in arange from 200 nm to 10 microns, although lesser and greater thicknessesmay also be employed. In one embodiment, the dielectric material layer4120 comprises a self-planarizing polymer material. In one embodiment,the dielectric material layer 4120 comprises a transparent material. Thetop surface of the dielectric material 4120 (which is a bottom surfaceof the dielectric material layer 4120 upon flipping the third exemplaryphotovoltaic structure) may be a planar surface, i.e., a surface that iswithin a flat plane.

A two-dimensional array of photovoltaic bristles (103, 104, 105, 107 a,106, 4122) is formed. Each photovoltaic bristle bristles (103, 104, 105,107 a, 106, 4122) comprises a vertically protruding portion of the layerstack (103, 104, 105, 107 a, 106) and embedding a dielectric core 4122comprising a dielectric material. The dielectric core 4122 contacts asidewall of the core conductive material layer 106. The transparentconductive material layer 103 is spaced from the core conductivematerial layer 106 by the photovoltaic material layer (104, 105).

Referring to FIG. 41B, a substrate, which is herein referred to as apassivation substrate 3770) is having a planar bottom surface may bedisposed on the top surface of the dielectric material layer 4120. Thepassivation substrate 3770 may be the same as in the first and secondexemplary photovoltaic structures. The passivation substrate 3770 may,or may not, be optically transparent. The passivation substrate 3770 mayinclude a material such as glass, sapphire, a polymer material, or aplastic material.

FIG. 41C is an exploded view of the third exemplary photovoltaicstructure after formation of the passivation substrate 3770. Thecombination of the sheet substrate 3710 and the moldable material layer3720 may be replaced with a moldable material layer 3820 that functionsas a substrate that provides mechanical support to provide a fourthexemplary photovoltaic structure. FIG. 41D provides a see-throughperspective view of the third or fourth exemplary photovoltaicstructure.

FIGS. 41E-41I are magnified views of various embodiments of aphotovoltaic bristle of the third exemplary photovoltaic structure. Thevarious dimensions such as a taper angle α, a base lateral dimension bd,a tapered-end lateral dimension td, the frustum height h1, and theheight h of the bristle 3700 may be the same as in the variousembodiments of the first exemplary photovoltaic structure. FIG. 41Eillustrates a photovoltaic bristle including a hemi-spheroid region.FIG. 41F illustrates a photovoltaic bristle including a substantiallyplanar top surface. FIG. 41F illustrates a photovoltaic bristleincluding a transparent conductive material as the material of the coreconductive material layer 106. FIG. 41H illustrates a photovoltaicbristle including a seam 3779 therein. FIG. 41I illustrates aphotovoltaic bristle including a via cavity 3769.

Referring to FIG. 42A, a fourth exemplary photovoltaic structure may bederived from the second exemplary photovoltaic structure of FIG. 38D bydepositing a dielectric material layer 4120 employing the sameprocessing steps of the processing steps of FIG. 41A. Thus, thecombination of the sheet substrate 3710 and the moldable material layer3720 is replaced with the moldable material layer 3820 that providesmechanical support to the photovoltaic bristles.

Each of the third and fourth exemplary photovoltaic structures may beflipped upside down prior to installation and/or use. In thisconfiguration, each of the third and fourth exemplary photovoltaicstructures comprises a dielectric material layer 4120 comprising aplanar portion having a uniform thickness and an array of protrudingportions 4122 extending from a planar surface of the planar portion; anda layer stack (103, 104, 105, 107 a, 106) located on the dielectricmaterial layer 4120 and comprising a core conductive material layer 106,a photovoltaic material layer (104, 105), and a transparent conductivematerial layer 103. The core conductive material layer 106 is in contactwith the planar surface and the protruding portions 4122 of thedielectric material layer 4120. The transparent conductive materiallayer 103 is spaced from the core conductive material layer 106 by thephotovoltaic material layer (104, 105). Each combination of a protrudingportion 4122 of the dielectric material layer 4120 and portions of thelayer stack (103, 104, 105, 107 a, 106) surrounding the protrudingportion 4122 constitutes a photovoltaic bristle (103, 104, 105, 107 a,106, 4122).

In one embodiment, the entirety of the dielectric material layer 4120may be a single material layer without any interface or seam therein. Inone embodiment, the entirety of the dielectric material layer 4120 mayhave a homogeneous material composition throughout. In one embodiment,the dielectric material layer 4120 comprises an optically transparentmaterial. In one embodiment, each protruding portion 4122 of thedielectric layer 4120 may have a variable horizontal cross-sectionalarea that decreases strictly with a vertical distance from the planarsurface of the planar portion of the dielectric material layer 4120. Inone embodiment, each protruding portion 4122 of the dielectric materiallayer 4120 may have a conical shape.

In one embodiment, a seam 3779 of the core conductive material layer 106may extend vertically from an apex of each protruding portion 4122 ofthe dielectric material layer 4120 as illustrated in FIG. 41H. In oneembodiment, a substrate (such as a passivation substrate 3770)contacting another planar surface of the planar portion of thedielectric material layer 4120 may be provided. Such a substrate 3770may be vertically spaced from the layer stack (103, 104, 105, 107 a,106) by the planar portion of the dielectric material layer 4120. In oneembodiment, each protruding portion 4122 may have a lateral dimensionless than 10 microns (which may be less than 5 microns, and may be, forexample, in a range from 10 nm to 3 microns) and a height less than 100microns (for example, in a range from 0.3 micron to 10 microns).

In one embodiment, the moldable material layer (3720, 3820) may be anoptically transparent layer. In this case, the optically transparentlayer (3720, 3820) may overlie, and laterally surround protrudingportions of, the layer stack (103, 104, 105, 107 a, 106). The entiretyof a top surface of the optically transparent layer (3720, 3820) (thatdoes not contact the layer stack) may be planar. In one embodiment, thesheet substrate 3710 may be a transparent substrate, which is located onthe top surface of the optically transparent layer (3720, 3820). In oneembodiment, the optically transparent layer (3720, 3820) may have arefractive index less than the refractive index of the transparentconductive material layer 103 to induce refraction at the interfacebetween the optically transparent layer (3720, 3820) and the transparentconductive material layer 103.

The optically transparent material of the optically transparent layer(3720, 3820) may be any transparent material that may be employed forthe moldable material layer (3720, 3820) of the first exemplaryphotovoltaic structure, or any transparent material that may be employedfor the moldable material layer 3820 of the second exemplaryphotovoltaic structure. In one embodiment, the optically transparentlayer (3720, 3820) comprises a polymer material. In one embodiment, theoptically transparent layer (3720, 3820) comprises a moldable materialselected from a lacquer, a silicone precursor material, a gel derivedfrom a sol containing a polymerizable colloid, and a glass transitionmaterial. In one embodiment, the optically transparent layer (3720,3820) comprises a moldable material selected from a polymer resin-basedplastic material, an organic material including at least one resin, aflexible glass material based on silica, phenylalkyl catechol-basedlacquers, nitrocellulose lacquers, acrylic lacquers, water-basedlacquers, silicone, a gel of silicon oxide, and a gel of dielectricmetal oxide. In one embodiment, the optically transparent layer (3720,3820) comprises a polymer material.

Referring to FIG. 43A, a fifth exemplary photovoltaic structure isillustrated during a manufacturing step. A sheet substrate 3710 and amoldable material layer 3720 having a uniform thickness may be providedas in the case of the first and third exemplary photovoltaic structures.For example, the moldable material layer 3720 may include an opticallytransparent material selected from a lacquer, a plastic material, aresin material, a silicone precursor material, a gel derived from a sol,and a glass transition material. The processing steps illustrated inFIG. 39 may be employed to patterning a top surface of the moldablematerial layer 3720 with an array pattern. In one embodiment, themoldable material layer 3720 may be patterned by imprinting a dieincluding a pattern of recessed structures and incorporated into a webonto the moldable material layer 3720. In one embodiment, the patternedmoldable material layer 3720 includes a pattern of dielectric cores3722. In one embodiment, the dielectric cores 3722 may be nanorods,which are structures each having a shape of a rod and having at leastone nanoscale dimension (i.e., a dimension less than 1 micron). Forexample, a diameter of a topmost portion of each dielectric core 3722may be less than 1 micron.

In this case, the array pattern may comprise a pattern of dielectriccores 3722 extending upward from the top surface of the moldablematerial layer 3720. Each dielectric core 3722 may be a patternedportion of the moldable material layer 3720. The array pattern includesan array of vertically extending shapes 3722 that protrude upward fromthat top surface of the moldable material layer 3720. Each verticallyextending shape 3720 may be a dielectric core 3722 of a respectivephotovoltaic bristle to be subsequently formed.

Referring to FIG. 43B, a layer stack (103, 104, 105, 107 a, 106) isdeposited over the array pattern. The layer stack comprises a coreconductive material layer 106, an optional inner transparent conductivelayer 107 a, a photovoltaic material layer (105, 104), and a transparentconductive material layer 103. Specifically, the core conductivematerial layer 106 may be deposited on the top surface of the planarportion of the moldable material layer 3720 and the dielectric cores3722 (vertically extending portions) of the moldable material layer3720. The optional inner transparent conductive layer 107 a may bedeposited on the core conductive material layer 106. The photovoltaicmaterial layer (105, 104) may be deposited on the optional innertransparent conductive layer 107 a and over the core conductive materiallayer 106. The transparent conductive material layer 103 may be formedon the photovoltaic material layer (105, 104). The thickness andcomposition of each layer within the layer stack (103, 104, 105, 107 a,106) may be the same as in the first, second, third, or fourth exemplaryphotovoltaic structures.

A two-dimensional array of photovoltaic bristles (103, 104, 105, 107 a,106, 3722) is formed. Each photovoltaic bristle (103, 104, 105, 107 a,106, 3722) comprises a vertically protruding portion of the layer stack(103, 104, 105, 107 a, 106) and embedding a dielectric core 3722comprising a dielectric material. The dielectric core 3722 contacts asidewall of the core conductive material layer 106. The transparentconductive material layer 103 is spaced from the core conductivematerial layer 106 by the photovoltaic material layer (105, 106).

Referring to FIG. 43C, a dielectric material layer 4320 is depositedover the layer stack (103, 104, 105, 107 a, 106). The dielectricmaterial layer 4320 may include any of the transparent materials thatmay be employed for the dielectric material layer 4210 of the third andfourth exemplary photovoltaic structures. In one embodiment, thedielectric material layer 4320 may include ethylene vinyl acetate. Thedielectric material layer 4320 may be deposited by a conformaldeposition method or a self-planarizing deposition method. The thicknessof the dielectric material layer 4320, as measured over a topmostsurface of the transparent conductive material layer 103, may be in arange from 0.5 micron to 20 microns, although lesser and greaterthicknesses may also be employed. The top surface of the dielectricmaterial layer 4320 may be planar as formed if a self-planarizingdeposition process (such as spin coating) is employed, or may beplanarized, for example, by polishing.

Subsequently, a passivation substrate 4310 having a planar bottomsurface may be disposed on a top surface of the dielectric materiallayer 4320. The passivation substrate 4320 comprises an opticallytransparent material. The passivation substrate 4320 may include amaterial such as glass, sapphire, an optically transparent polymermaterial, or an optically transparent plastic material.

FIG. 43D is an exploded view of the fifth exemplary photovoltaicstructure after formation of the passivation substrate 4310. Thecombination of the sheet substrate 3710 and the moldable material layer3720 may be replaced with a moldable material layer 3820 that functionsas a substrate that provides mechanical support to provide a sixthexemplary photovoltaic structure. FIG. 43E provides a see-throughperspective view of the fifth or sixth exemplary photovoltaic structure.

FIGS. 44A-44C are magnified views of various embodiments of aphotovoltaic bristle of the fifth exemplary photovoltaic structure. Thevarious dimensions such as a taper angle α, a base lateral dimension bd,a tapered-end lateral dimension td, the frustum height h1, and theheight h of the bristle 3700 may be the same as in the variousembodiments of the first exemplary photovoltaic structure. FIG. 44Aillustrates a photovoltaic bristle including a hemi-spheroid region.FIG. 44B illustrates a photovoltaic bristle including a substantiallyplanar top surface. FIG. 44C illustrates a photovoltaic bristleincluding a transparent conductive material as the material of the coreconductive material layer 106.

Referring to FIG. 45, a sixth exemplary photovoltaic structure may bederived from the fifth exemplary photovoltaic structure by substitutinga moldable material layer 3820 for a combination of a sheet substrate3710 and a moldable material layer 3820. In other words, the combinationof the sheet substrate 3710 and the moldable material layer 3720 of thefifth exemplary photovoltaic structure is replaced with the moldablematerial layer 3820 that provides mechanical support to the photovoltaicbristles of the sixth exemplary photovoltaic structure.

Each of the fifth and sixth exemplary photovoltaic structures comprisesa dielectric material layer (3720, 3820), which is a moldable materiallayer. The dielectric material layer (3720, 3820) comprises a planarportion having a uniform thickness and an array of protruding portions3722 extending from a planar surface of the planar portion; and a layerstack (103, 104, 105, 107 a, 106) located on the dielectric materiallayer (3720, 3820) and comprising a core conductive material layer 106,a photovoltaic material layer (104, 105), and a transparent conductivematerial layer 103. The core conductive material layer 106 is in contactwith the planar surface and the protruding portions 3722 of thedielectric material layer (3720, 3820). The transparent conductivematerial layer 103 is spaced from the core conductive material layer 106by the photovoltaic material layer (104, 105). Each combination of aprotruding portion 3722 of the dielectric material layer (3720, 3820)and portions of the layer stack (103, 104, 105, 107 a, 106) surroundingthe protruding portion 3722 constitutes a photovoltaic bristle (103,104, 105, 107 a, 106, 3722).

In one embodiment, the dielectric material layer (3720, 3820) comprisesa self-planarizing polymer material, which forms a film of a uniformthickness prior to imprinting, and is subsequently cured to provide thedielectric cores 3722 that do not change shapes. In one embodiment, thedielectric material layer (3720, 3820) comprises an opticallytransparent material. The core conductive material layer 106 isdeposited on surfaces of the dielectric cores 3722 and the top surfaceof the planar portion of the dielectric material layer (3720, 3820),i.e., the moldable material layer. The photovoltaic material layer (104,105) is deposited on the core conductive material layer 106. Thetransparent conductive material layer 103 is deposited on thephotovoltaic material layer (104, 105).

In one embodiment, the entirety of the dielectric material layer (3720,3820) may be a single material layer without any interface or seamtherein. In one embodiment, the entirety of the dielectric materiallayer (3720, 3820) may have a homogeneous material compositionthroughout. In one embodiment, the dielectric material layer (3720,3820) comprises an optically transparent material. In one embodiment,each protruding portion (i.e., each dielectric core 3722) of thedielectric material layer (3720, 3820) may have a variable horizontalcross-sectional area that decreases strictly with a vertical distancefrom the planar surface of the planar portion of the dielectric materiallayer (3720, 3820). In one embodiment, each protruding portion of thedielectric material layer may have a conical shape.

In one embodiment, a substrate (e.g., a sheet substrate 3710) contactinganother planar surface of the planar portion of the dielectric materiallayer 3720 and vertically spaced from the layer stack (103, 104, 105,107 a, 106) by the planar portion of the dielectric material layer 3720.In one embodiment, each protruding portion 3722 may have a lateraldimension less than 10 microns and a height less than 100 microns.

In one embodiment, an optically transparent layer 4320 may overlie thelayer stack (103, 104, 105, 107 a, 106). The entirety of the top surfaceof the optically transparent layer 4320 may be planar. A transparentsubstrate (such as a passivation substrate 4310) may be located on thetop surface of the optically transparent layer 4320. The opticallytransparent layer 4320 may have a refractive index less than arefractive index of the transparent conductive material layer 103. Inone embodiment, the optically transparent layer 4320 may comprise apolymer material, which may be any transparent material that may beemployed for the dielectric material layer 4120 discussed above.

In one embodiment, the dielectric material layer (3720, 3820) of thefifth or sixth exemplary photovoltaic structure may comprise a moldablematerial selected from a lacquer, a silicone precursor material, a gelderived from a sol containing a polymerizable colloid, and a glasstransition material. In one embodiment, the dielectric material layer(3720, 3820) comprises a moldable material selected from a polymerresin-based plastic material, an organic material including at least oneresin, a flexible glass material based on silica, phenylalkylcatechol-based lacquers, nitrocellulose lacquers, acrylic lacquers,water-based lacquers, silicone, a gel of silicon oxide, and a gel ofdielectric metal oxide. In one embodiment, the dielectric material layer(3720, 3820) comprises a polymer material.

The preceding description of the disclosed embodiments is provided toenable any person skilled in the art to make or use the presentinvention. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments without departing from thespirit or scope of the invention. Thus, the present invention is notintended to be limited to the embodiments shown herein but is to beaccorded the widest scope consistent with the following claims and theprinciples and novel features disclosed herein.

What is claimed is:
 1. A photovoltaic structure comprising: a dielectricmaterial layer comprising a planar portion having a uniform thicknessand an array of protruding portions extending from a planar surface ofthe planar portion; and a layer stack located on the dielectric materiallayer and comprising a core conductive material layer, a photovoltaicmaterial layer, and a transparent conductive material layer, wherein:the core conductive material layer is in contact with the planar surfaceand the protruding portions of the dielectric material layer; thetransparent conductive material layer is spaced from the core conductivematerial layer by the photovoltaic material layer; and each combinationof a protruding portion of the dielectric material layer and portions ofthe layer stack surrounding the protruding portion constitutes aphotovoltaic bristle.
 2. The photovoltaic structure of claim 1, whereinan entirety of the dielectric material layer is a single material layerwithout any interface or seam therein.
 3. The photovoltaic structure ofclaim 1, wherein an entirety of the dielectric material layer has ahomogeneous material composition throughout.
 4. The photovoltaicstructure of claim 1, wherein the dielectric material layer comprises anoptically transparent material.
 5. The photovoltaic structure of claim1, wherein each protruding portion of the dielectric layer has avariable horizontal cross-sectional area that decreases strictly with avertical distance from the planar surface of the planar portion of thedielectric layer.
 6. The photovoltaic structure of claim 5, wherein eachprotruding portion of the dielectric layer has a conical shape.
 7. Thephotovoltaic structure of claim 5, wherein a seam of the core conductivematerial layer extends vertically from an apex of each protrudingportion of the dielectric material layer.
 8. The photovoltaic structureof claim 1, further comprising a substrate contacting another planarsurface of the planar portion of the dielectric material layer andvertically spaced from the layer stack by the planar portion of thedielectric material layer.
 9. The photovoltaic structure of claim 1,wherein each protruding portion has a lateral dimension less than 10microns and a height less than 100 microns.
 10. The photovoltaicstructure of claim 1, further comprising an optically transparent layeroverlying the layer stack, wherein an entirety of a top surface of theoptically transparent layer is planar.
 11. The photovoltaic structure ofclaim 10, further comprising a transparent substrate located on the topsurface of the optically transparent layer.
 12. The photovoltaicstructure of claim 10, wherein the optically transparent layer has arefractive index less than a refractive index of the transparentconductive material layer.
 13. The photovoltaic structure of claim 10,wherein the optically transparent layer comprises a polymer material.14. The photovoltaic structure of claim 1, wherein the dielectricmaterial layer comprises a moldable material selected from a lacquer, asilicone precursor material, a gel derived from a sol containing apolymerizable colloid, and a glass transition material.
 15. Thephotovoltaic structure of claim 1, wherein the dielectric material layercomprises a moldable material selected from a polymer resin-basedplastic material, an organic material including at least one resin, aflexible glass material based on silica, a phenylalkyl catechol-basedlacquers, nitrocellulose lacquers, acrylic lacquers, water-basedlacquers, silicone, a gel of silicon oxide, and a gel of dielectricmetal oxide.
 16. The photovoltaic structure of claim 1, wherein thedielectric material layer comprises a polymer material.
 17. A method offorming a photovoltaic structure, comprising: patterning a top surfaceof a moldable material layer with an array pattern, the array patternincluding an array of vertically extending shapes that protrude upwardor downward from that top surface of the moldable material layer;depositing a layer stack over the array pattern, the layer stackcomprising a transparent conductive material layer, a photovoltaicmaterial layer, and a core conductive material layer; and depositing adielectric material layer over the layer stack, wherein: atwo-dimensional array of photovoltaic bristles is formed, eachphotovoltaic bristle comprising a vertically protruding portion of thelayer stack and embedding a dielectric core comprising a dielectricmaterial; the dielectric core contacts a sidewall of the core conductivematerial layer; and the transparent conductive material layer is spacedfrom the core conductive material layer by the photovoltaic materiallayer.
 18. The method of claim 17, further comprising disposing apassivation substrate having a planar bottom surface on a top surface ofthe dielectric material layer.
 19. The method of claim 17, wherein eachdielectric core has a variable horizontal cross-sectional area thatdecreases with a vertical distance from the top surface of the moldablematerial layer.
 20. The method of claim 19, wherein each dielectric corehas a conical shape.
 21. The method of claim 17, wherein the moldablematerial layer an optically transparent material selected from alacquer, a plastic material, a resin material, a silicone precursormaterial, a gel derived from a sol, and a glass transition material. 22.The method of claim 17, wherein the dielectric material layer comprisesa self-planarizing polymer material.
 23. The method of claim 17, whereinthe array pattern comprises a pattern of via cavities extending downwardfrom the top surface of the moldable material layer.
 24. The method ofclaim 23, wherein each dielectric core is a portion of the dielectricmaterial layer that protrudes into a respective via cavity.
 25. Themethod of claim 23, wherein each via cavity is entirely filled with arespective photovoltaic bristle.
 26. The method of claim 23, furthercomprising: depositing the core conductive material layer on surfaces ofthe via cavities and the top surface of the moldable material layer;depositing the photovoltaic material layer on the core conductivematerial layer; and depositing the transparent conductive material layeron the photovoltaic material layer.
 27. The method of claim 17, whereinthe array pattern comprises a pattern of dielectric cores extendingupward from the top surface of the moldable material layer.
 28. Themethod of claim 27, wherein each dielectric core is a patterned portionof the moldable material layer.
 29. The method of claim 27, wherein thedielectric material layer comprises an optically transparent material.30. The method of claim 22, further comprising: depositing the coreconductive material layer on surfaces of the dielectric cores and thetop surface of the moldable material layer; depositing the photovoltaicmaterial layer on the core conductive material layer; and depositing thetransparent conductive material layer on the photovoltaic materiallayer.
 31. The method of claim 17, wherein the moldable material layeris patterned by imprinting a die including a pattern of protrudingstructures and incorporated into a web onto the moldable material layer,wherein the patterned moldable material layer includes a pattern of viacavities.
 32. The method of claim 17, wherein the moldable materiallayer is patterned by imprinting a die including a pattern of recessedstructures and incorporated into a web onto the moldable material layer,wherein the patterned moldable material layer includes a pattern ofnanorods.
 33. The method of claim 17, wherein: the moldable materiallayer is provided by applying a polymerizable material on a substrateand inducing partial polymerization of the polymerizable material; andthe patterned moldable material layer is cured for furtherpolymerization prior to depositing the layer stack.
 34. A method formanufacturing a metamaterial including an array of photovoltaic bristleshaving approximately cylindrical shapes, comprising: forming an array ofvias extending into a substrate, wherein each via within the array hasan approximately cylindrical shape and is laterally separated from oneanother, and is laterally surrounded, by the substrate; depositing atransparent conductive layer over the array of vias; depositing anabsorber layer over the outer conductive layer; depositing a coreconductive material layer over the absorber layer, wherein each via ispartially filled with the core conductive material layer to form aconductive core of a respective photovoltaic bristle; filling cavitieswithin the vias by depositing a dielectric material layer over the coreconductive material layer; and forming a base layer over the depositedconductive material, wherein a dielectric core that comprises thedielectric material is formed within each photovoltaic bristle andbetween the core conductive material layer and the base layer.
 35. Themethod of claim 34, wherein: the substrate comprises a moldablematerial; and the array of vias is formed by moving the moldablematerial under a rolling press or under a rolling die that transfers apattern thereupon on the moldable material.
 36. The method of claim 34,wherein the transparent conductive layer comprises transparentconductive oxide or transparent conductive nitride.
 37. The method ofclaim 34, further comprising forming a transparent non-conductiveoptically transparent layer over the array of vias.
 38. The method ofclaim 34, wherein the substrate comprises a polymer.